I tried to reproduce this by booting a natty live system, manually enabling multiarch (/etc/dpkg/dpkg.cfg.d/multiarch), and upgrading to oneiric's libc6, libglib2.0-*, and then installing libglib2.0-0:i386. These steps all worked fine, and changelog.Debian.gz for all glib2.0 binaries were intact after each step.
I tried to reproduce this by booting a natty live system, manually enabling multiarch (/etc/dpkg/ dpkg.cfg. d/multiarch) , and upgrading to oneiric's libc6, libglib2.0-*, and then installing libglib2.0-0:i386. These steps all worked fine, and changelog.Debian.gz for all glib2.0 binaries were intact after each step.