This sounds pretty cool...
In an exclusive article,
http://www.eurogamer.net/article.php?article_id=55290 dives into the XBox version of Doom and discovers some very interesting details about the multiplayer side.
"The Xbox version of Doom III currently in development at Vicarious Visions will feature co-operative online play via Xbox Live, according to word coming out of an Activision press event in California today. Our source on the scene reports that it "looks great" up and running, and that the four-player Live deathmatch mode is also quite something to behold."