Interesting problem - we've got a similar situation here, but I like to keep two copies of the music files on two different computers anyway, for backup. If all the client computers are running Windows, would it be possible to install and run iTunes itself on the Samba share? That supposes it can be convinced to store the user preferences on the share, and use those preferences, whoever is running it...

I found an Applescript (http://crossroads.net/a/2005/02/14/multiple_itunes_libraries_one_music_folder) to do this (via ipodlounge (http://forums.ipodlounge.com/archive/topic/74013-1.html)) but this is Mac only. Maybe browse the ipodlounge forums, or the forums on Apple support, ... eek! I see you've already discovered the latter!