To the best of my knowledge you only need the CD in the drive to load the game, so you put the CD in one computer, load the game, take the CD out, put it in a different computer, load the game and rinse and repeat.
Since you don't need the CD to actually start or join a session this should work if the computers are in close proximity to each other. This might cause some slow down though have only tried it briefly at my home over my network.