Yes, it is possible.
I have a Lacie 120G d2 drive with all of my mp3's on which i share between two mac's running 10.2.5 and 9.2.2.
The easiest way i found is if you set the defualt iTunes music folder for importing/library to the desired music folder on the external drive for all installations of iTunes and keep a master copy of your playlists and do the same for them.
As far as a shared network drive, i haven't tried it but i don't see why it shouldn't work as long as the ext drive volume is mounted on all respective comps - and itunes allows it.
Although if you wait till next thursday when rendevouz playlists arrive your situation will more than likely be, either answered beyond your wildest dreams, and/or dashed/delayed by the inconvienence of needing everything that will be announced.
Hope this answers your question.
If you have any probs just PM me.
