Comment 2 for bug 334472

I don't think this is the right way to do it. It sounds like a icky thing to do, since human-icon-theme inherit gnome-icon-theme already, so you'll have a circular dependency kind off.
It will also deepen the gap between upstream and ubuntu's gnome-icon-theme (the only difference I can think of right now is that the start-here icon is changed), and that will open up to more bugs and confused maintainers.

A better solution is to make notifyosd install the icons into it's private hicolor, just like banshee, rhythmbox, gpm etc. currently does (ie /usr/share/notifyosd/icons/$size/status). More instructions here:
http://live.gnome.org/ThemableAppSpecificIcons/