You can get songs into the library without importing the actual files. I guess you would need the files in some shared drive and individuals imort the ones they want into their libraries. And have them set to rip files into the shared folder. More info maybe when I'm in front of my mac - till then here's the result of a quick search. (There's lots of mac help stuff on the web)
http://forums.macrumors.com/archive/...p/t-50033.html
Editted to say - Yes there's a setting in preferences that allows you to import the tracks into your library but not actually import the files into your itunes folder. Incidentally, you can access the prefernecs for all mac progs the same way - click the program name in the bar at the top of the screen (it's only there if that window is the active one) and select preferences.