Comment 2 for bug 703769

Old DBusGProxys did emit "destroy" when a unique owner died:

"This proxy will only emit the "destroy" signal if the DBusConnection is disconnected, the proxy has no remaining references, or the name is a unique name and its owner disappears. If a well-known name changes owner, the proxy will still be alive."

You're right that notify::g-name-owner does not get emitted for owner changes on unique names though. I missed that here.

Instead of linking and using bamf, I think the better thing to do is to use g_bus_watch_name and friends, which promise to work on unique names. I'll look at that.