Field Operative published a guide to getting all your friends on to one team in Battlefield Bad Company 2 on Xbox 360. If you use use the private chat feature of Xbox Live you can talk to all of your team! It will take a while to get everyone on the same team because of the limitations of the game but it can be done. It must be quite amazing to play on a team of 12 who are coordinated and following one single strategy.
Unfortunately a similar chat feature doesn’t exist on the PS3 but friends can still join the session if the game has free slots.