http://psp.ign.com/articles/552/552955p1.html
The PSP version of Tokyo Xtreme is a bit different from its console predecessors in that players now race as part of a team that longs to control Tokyo's highways. The game actually has numerous teams, each controlling part of the fifteen sections that make up the Tokyo highway system featured in the game. You select your team at the start of the game and help to make the team rule the roads while attempting to become team leader.
Two forms of battle feature in the game. Ranking Battles are races between members of the same team. By defeating your team members, you climb the ranks of your team and eventually arrive at the leader position.
Being leader is important for the other type of battle, Team Battle. In these battles, the leader of a team chooses up to five representatives of his team to race against up to five representatives of another team. These races are one-on-one, with the last team standing taking the prize. Defeating other teams in this fashion is the key to gaining control over new areas of the highway.
The best part about all of this is that it's going to be playable in multiplayer form via the PSP's wireless networking functionality. In network mode, teams will be comprised of real players who must race one another in Ranking Battles in order to become leader. The leader of a team then goes on to assign other real-life players to race against other teams in Team Battles.