I still encountered a failure beginning with Ubuntu GNOME Trusty i386 w/Vivid HWE. There was a kernel upgrade prior to performing the HWE upgrade (most recent prior updates performed on 2016-08-07 followed by installing update-manager from proposed):

Start-Date: 2016-08-13  09:58:41
Commandline: apt-get dist-upgrade
Install: linux-headers-3.19.0-66:i386 (3.19.0-66.74~14.04.1, automatic), linux-headers-3.19.0-66-generic:i386 (3.19.0-66.74~14.04.1, automatic), linux-image-3.19.0-66-generic:i386 (3.19.0-66.74~14.04.1, automatic), linux-image-extra-3.19.0-66-generic:i386 (3.19.0-66.74~14.04.1, automatic)
Upgrade: nautilus-data:i386 (3.10.1-0ubuntu9.9, 3.10.1-0ubuntu9.11), modemmanager:i386 (1.0.0-2ubuntu1, 1.0.0-2ubuntu1.1), initramfs-tools:i386 (0.103ubuntu4.3, 0.103ubuntu4.4), linux-generic-lts-vivid:i386 (3.19.0.65.47, 3.19.0.66.48), libmm-glib0:i386 (1.0.0-2ubuntu1, 1.0.0-2ubuntu1.1), firefox:i386 (47.0+build3-0ubuntu0.14.04.1, 48.0+build2-0ubuntu0.14.04.1), libgd3:i386 (2.1.0-3ubuntu0.2, 2.1.0-3ubuntu0.3), libdrm-intel1:i386 (2.4.64-1~ubuntu14.04.1, 2.4.67-1ubuntu0.14.04.1), avahi-autoipd:i386 (0.6.31-4ubuntu1, 0.6.31-4ubuntu1.1), libcurl3:i386 (7.35.0-1ubuntu2.6, 7.35.0-1ubuntu2.8), oxideqt-codecs-extra:i386 (1.15.8-0ubuntu0.14.04.1, 1.16.5-0ubuntu0.14.04.1), grub-common:i386 (2.02~beta2-9ubuntu1.11, 2.02~beta2-9ubuntu1.12), libdrm-radeon1:i386 (2.4.64-1~ubuntu14.04.1, 2.4.67-1ubuntu0.14.04.1), nautilus:i386 (3.10.1-0ubuntu9.9, 3.10.1-0ubuntu9.11), isc-dhcp-client:i386 (4.2.4-7ubuntu12.4, 4.2.4-7ubuntu12.5), grub-pc:i386 (2.02~beta2-9ubuntu1.11, 2.02~beta2-9ubuntu1.12), libnautilus-extension1a:i386 (3.10.1-0ubuntu9.9, 3.10.1-0ubuntu9.11), libavahi-common-data:i386 (0.6.31-4ubuntu1, 0.6.31-4ubuntu1.1), libxrandr2:i386 (1.4.2-1, 1.5.0-1~trusty1), libavahi-client3:i386 (0.6.31-4ubuntu1, 0.6.31-4ubuntu1.1), libdrm2:i386 (2.4.64-1~ubuntu14.04.1, 2.4.67-1ubuntu0.14.04.1), base-files:i386 (7.2ubuntu5.4, 7.2ubuntu5.5), language-pack-gnome-en:i386 (14.04+20150219, 14.04+20160720), libavahi-common3:i386 (0.6.31-4ubuntu1, 0.6.31-4ubuntu1.1), libdrm-nouveau2:i386 (2.4.64-1~ubuntu14.04.1, 2.4.67-1ubuntu0.14.04.1), language-pack-en:i386 (14.04+20150219, 14.04+20160720), linux-libc-dev:i386 (3.13.0-92.139, 3.13.0-93.140), avahi-utils:i386 (0.6.31-4ubuntu1, 0.6.31-4ubuntu1.1), grub2-common:i386 (2.02~beta2-9ubuntu1.11, 2.02~beta2-9ubuntu1.12), avahi-daemon:i386 (0.6.31-4ubuntu1, 0.6.31-4ubuntu1.1), grub-pc-bin:i386 (2.02~beta2-9ubuntu1.11, 2.02~beta2-9ubuntu1.12), libavahi-gobject0:i386 (0.6.31-4ubuntu1, 0.6.31-4ubuntu1.1), libcurl3-gnutls:i386 (7.35.0-1ubuntu2.6, 7.35.0-1ubuntu2.8), libavahi-glib1:i386 (0.6.31-4ubuntu1, 0.6.31-4ubuntu1.1), language-pack-en-base:i386 (14.04+20150219, 14.04+20160720), initramfs-tools-bin:i386 (0.103ubuntu4.3, 0.103ubuntu4.4), firefox-locale-en:i386 (47.0+build3-0ubuntu0.14.04.1, 48.0+build2-0ubuntu0.14.04.1), isc-dhcp-common:i386 (4.2.4-7ubuntu12.4, 4.2.4-7ubuntu12.5), linux-headers-generic-lts-vivid:i386 (3.19.0.65.47, 3.19.0.66.48), linux-image-generic-lts-vivid:i386 (3.19.0.65.47, 3.19.0.66.48), language-pack-gnome-en-base:i386 (14.04+20150219, 14.04+20160720), libavahi-core7:i386 (0.6.31-4ubuntu1, 0.6.31-4ubuntu1.1)
End-Date: 2016-08-13  10:31:06

I didn't see anything odd in hwe-support-status so accepted the upgrade:

Start-Date: 2016-08-13  11:02:05
Commandline: aptdaemon role='role-commit-packages' sender=':1.82'
Install: xserver-xorg-input-synaptics-lts-xenial:i386 (1.8.2-1ubuntu3~trusty1, automatic), libgl1-mesa-dri-lts-xenial:i386 (11.2.0-1ubuntu2~trusty1, automatic), xserver-xorg-video-amdgpu-lts-xenial:i386 (1.1.0-1~trusty1, automatic), linux-headers-4.4.0-34-generic:i386 (4.4.0-34.53~14.04.1, automatic), libgles2-mesa-lts-xenial:i386 (11.2.0-1ubuntu2~trusty1), xserver-xorg-video-qxl-lts-xenial:i386 (0.1.4-3ubuntu3~trusty1, automatic), xserver-xorg-video-savage-lts-xenial:i386 (2.3.8-1ubuntu3~trusty1, automatic), xserver-xorg-video-trident-lts-xenial:i386 (1.3.7-1build2~trusty1, automatic), xserver-xorg-video-siliconmotion-lts-xenial:i386 (1.7.8-1ubuntu6~trusty1, automatic), libegl1-mesa-lts-xenial:i386 (11.2.0-1ubuntu2~trusty1), xserver-xorg-lts-xenial:i386 (7.7+13ubuntu3~trusty2), xserver-xorg-input-vmmouse-lts-xenial:i386 (13.1.0-1ubuntu2~trusty1, automatic), xserver-xorg-video-r128-lts-xenial:i386 (6.10.0-1build2~trusty1, automatic), libglapi-mesa-lts-xenial:i386 (11.2.0-1ubuntu2~trusty1, automatic), xserver-xorg-video-nouveau-lts-xenial:i386 (1.0.12-1build2~trusty1, automatic), xserver-xorg-input-wacom-lts-xenial:i386 (0.32.0-0ubuntu3~trusty1, automatic), linux-generic-lts-xenial:i386 (4.4.0.34.24), xserver-xorg-video-openchrome-lts-xenial:i386 (0.3.3+git20160310-1~trusty1, automatic), xserver-xorg-input-all-lts-xenial:i386 (7.7+13ubuntu3~trusty2), xserver-xorg-video-neomagic-lts-xenial:i386 (1.2.9-1build2~trusty1, automatic), xserver-xorg-video-vesa-lts-xenial:i386 (2.3.4-1build2~trusty1, automatic), xserver-xorg-input-evdev-lts-xenial:i386 (2.10.1-1ubuntu2~trusty1, automatic), libllvm3.8v4:i386 (3.8-2ubuntu3~trusty4, automatic), xserver-xorg-video-vmware-lts-xenial:i386 (13.1.0-2ubuntu3~trusty1, automatic), xserver-xorg-video-mach64-lts-xenial:i386 (6.9.5-1build2~trusty1, automatic), linux-image-extra-4.4.0-34-generic:i386 (4.4.0-34.53~14.04.1, automatic), linux-headers-4.4.0-34:i386 (4.4.0-34.53~14.04.1, automatic), linux-image-4.4.0-34-generic:i386 (4.4.0-34.53~14.04.1, automatic), xserver-xorg-video-radeon-lts-xenial:i386 (7.7.0-1~trusty2, automatic), xserver-xorg-video-tdfx-lts-xenial:i386 (1.4.6-1build2~trusty1, automatic), xserver-xorg-video-fbdev-lts-xenial:i386 (0.4.4-1build5~trusty1, automatic), libgl1-mesa-glx-lts-xenial:i386 (11.2.0-1ubuntu2~trusty1), xserver-xorg-video-intel-lts-xenial:i386 (2.99.917+git20160325-1ubuntu1~trusty1, automatic), libgbm1-lts-xenial:i386 (11.2.0-1ubuntu2~trusty1, automatic), xserver-xorg-video-mga-lts-xenial:i386 (1.6.4-1build2~trusty1, automatic), libllvm3.4:i386 (3.4-1ubuntu3), libdrm-amdgpu1:i386 (2.4.67-1ubuntu0.14.04.1), linux-headers-generic-lts-xenial:i386 (4.4.0.34.24, automatic), linux-image-generic-lts-xenial:i386 (4.4.0.34.24, automatic), libglamor0:i386 (0.6.0-0ubuntu4), libxatracker2-lts-xenial:i386 (11.2.0-1ubuntu2~trusty1), xserver-xorg-video-all-lts-xenial:i386 (7.7+13ubuntu3~trusty2, automatic), libgles1-mesa-lts-xenial:i386 (11.2.0-1ubuntu2~trusty1), xserver-xorg-video-sisusb-lts-xenial:i386 (0.9.6-2build5~trusty1, automatic), xserver-xorg-core-lts-xenial:i386 (1.18.3-1ubuntu2.2~trusty2), xserver-xorg-video-cirrus-lts-xenial:i386 (1.5.3-1ubuntu3~trusty1, automatic), xserver-xorg-video-ati-lts-xenial:i386 (7.7.0-1~trusty2, automatic)
Upgrade: libpam-gnome-keyring:i386 (3.10.1-1ubuntu4.2, 3.10.1-1ubuntu4.3), update-notifier:i386 (0.154.1ubuntu1, 0.154.1ubuntu2), libdevmapper1.02.1:i386 (1.02.77-6ubuntu2, 1.02.77-6ubuntu3), lsb-base:i386 (4.1+Debian11ubuntu6.1, 4.1+Debian11ubuntu6.2), gnome-contacts:i386 (3.8.3-1ubuntu1, 3.8.3-1ubuntu1.1), dmsetup:i386 (1.02.77-6ubuntu2, 1.02.77-6ubuntu3), update-manager:i386 (0.196.16, 0.196.18), gnome-keyring:i386 (3.10.1-1ubuntu4.2, 3.10.1-1ubuntu4.3), parted:i386 (2.3-19ubuntu1.14.04.1, 2.3-19ubuntu1.14.04.2), libdevmapper-event1.02.1:i386 (1.02.77-6ubuntu2, 1.02.77-6ubuntu3), linux-libc-dev:i386 (3.13.0-93.140, 3.13.0-94.141), python3-update-manager:i386 (0.196.16, 0.196.18), lsb-release:i386 (4.1+Debian11ubuntu6.1, 4.1+Debian11ubuntu6.2), update-notifier-common:i386 (0.154.1ubuntu1, 0.154.1ubuntu2), duplicity:i386 (0.6.23-1ubuntu4.1, 0.6.23-1ubuntu4.2), update-manager-core:i386 (0.196.16, 0.196.18), libparted0debian1:i386 (2.3-19ubuntu1.14.04.1, 2.3-19ubuntu1.14.04.2), libp11-kit-gnome-keyring:i386 (3.10.1-1ubuntu4.2, 3.10.1-1ubuntu4.3)
Remove: libgbm1-lts-vivid:i386 (10.5.9-2ubuntu1~trusty2), xserver-xorg-input-mouse-lts-vivid:i386 (1.9.1-1~trusty1), libgles2-mesa-lts-vivid:i386 (10.5.9-2ubuntu1~trusty2), xserver-xorg-video-intel-lts-vivid:i386 (2.99.917-1~exp1ubuntu2.2~trusty1), xserver-xorg-core-lts-vivid:i386 (1.17.1-0ubuntu3.1~trusty1.1), xserver-xorg-video-nouveau-lts-vivid:i386 (1.0.11-1ubuntu2build1~trusty1), xserver-xorg-video-all-lts-vivid:i386 (7.7+7ubuntu3~trusty1), xserver-xorg-video-sisusb-lts-vivid:i386 (0.9.6-2build3~trusty1), xserver-xorg-video-ati-lts-vivid:i386 (7.5.0-1ubuntu2~trusty1), xserver-xorg-video-siliconmotion-lts-vivid:i386 (1.7.7-2ubuntu2~trusty1), libxatracker2-lts-vivid:i386 (10.5.9-2ubuntu1~trusty2), xserver-xorg-video-r128-lts-vivid:i386 (6.9.2-1ubuntu1~trusty1), xserver-xorg-video-vmware-lts-vivid:i386 (13.1.0-0ubuntu1build1~trusty1), libwayland-egl1-mesa-lts-vivid:i386 (10.5.9-2ubuntu1~trusty2), libgl1-mesa-dri-lts-vivid:i386 (10.5.9-2ubuntu1~trusty2), libegl1-mesa-lts-vivid:i386 (10.5.9-2ubuntu1~trusty2), xserver-xorg-lts-vivid:i386 (7.7+7ubuntu3~trusty1), xserver-xorg-video-trident-lts-vivid:i386 (1.3.6-0ubuntu6build1~trusty1), xserver-xorg-video-cirrus-lts-vivid:i386 (1.5.2-2ubuntu1~trusty1), xserver-xorg-video-tdfx-lts-vivid:i386 (1.4.6-0ubuntu1~trusty1), xserver-xorg-input-wacom-lts-vivid:i386 (0.25.0-0ubuntu1.1~trusty1), xserver-xorg-video-mach64-lts-vivid:i386 (6.9.4-2ubuntu1~trusty1), xserver-xorg-video-mga-lts-vivid:i386 (1.6.3-2ubuntu1~trusty1), xserver-xorg-input-all-lts-vivid:i386 (7.7+7ubuntu3~trusty1), libgl1-mesa-glx-lts-vivid:i386 (10.5.9-2ubuntu1~trusty2), xserver-xorg-video-vesa-lts-vivid:i386 (2.3.3-1build3~trusty1), xserver-xorg-video-fbdev-lts-vivid:i386 (0.4.4-1build3~trusty1), xserver-xorg-input-vmmouse-lts-vivid:i386 (13.0.0-1ubuntu1~trusty1), xserver-xorg-video-openchrome-lts-vivid:i386 (0.3.3-1ubuntu1~trusty1), xserver-xorg-video-radeon-lts-vivid:i386 (7.5.0-1ubuntu2~trusty1), xserver-xorg-video-savage-lts-vivid:i386 (2.3.7-2ubuntu4~trusty1), xserver-xorg-input-synaptics-lts-vivid:i386 (1.8.1-1ubuntu1~trusty1), xserver-xorg-input-evdev-lts-vivid:i386 (2.9.0-1ubuntu2~trusty1), xserver-xorg-video-neomagic-lts-vivid:i386 (1.2.8-1ubuntu1~trusty1), libglapi-mesa-lts-vivid:i386 (10.5.9-2ubuntu1~trusty2), libgles1-mesa-lts-vivid:i386 (10.5.9-2ubuntu1~trusty2)
End-Date: 2016-08-13  11:21:51

But libwayland-egl1-mesa-lts-xenial had not installed:

Start-Date: 2016-08-13  11:49:00
Commandline: apt-get install libwayland-egl1-mesa-lts-xenial
Install: libwayland-egl1-mesa-lts-xenial:i386 (11.2.0-1ubuntu2~trusty1)
End-Date: 2016-08-13  11:49:05

In retrospect I did NOT upgrade update-notifier prior to beginning the test but to get the GUI informing of the HWE upgrade I re-enabled proposed. So the HWE upgrade was performed with proposed enabled.