Ill just quote this guy from the MB forums who got the idea of trying to get Xfire support Movie Battles.. (if u think this is advertising, move it to that forum but imo it isnt):
Jedi Vader;406769Hey i'm trying to get XFire support for MB2. Just reply to the following thread and say "Support!". If a lot of people do it, there's definitely a chance. The people at XFire listen to their community.
4th September 2005
Don't waste your time, Xfire have said time and time again that they don't add support for mods, since they use the same executable as the game.
I don't know how, and I don't know why, but this is totally Sheep's fault.
Garrys mod is supported..
Lets call LA then xD
Pimp of FileFront.
30th January 2008
You can tell if someone is playing MB2 anyway, click on the name and (since most servers now use the map >.>) it will say mb_dotf as the map name.