Comment 3 for bug 998388

I can confirm that '/etc/network/if-down.d/upstart' is NOT executed when any interface is down.

I've added a simple test line to test it:

       echo "`date` - $0 - $IFACE - $METHOD" >> "/tmp/upstart.log"

and no file is created.

I've also found a workaround, if I create a link in '/etc/network/if-post-down.d/' it works. so for now, if anyone is interested, you can execute

     ln -s /etc/network/if-down.d/upstart /etc/network/if-post-down.d/upstart

and you'll get desired behaviour.

I'm still waiting for some dev to confirm this bug