I think It's pretty obvious that we aren't seeing any of the single player characters in the multiplayer footage. They said there was a campaign, so that's where the story is gonna be at. For multiplayer, we get the different cars, all driven by dollface and sweettooth minions. Kinda genius really.
Few other things I noticed.
-Swarm missles seem to be back. (one of the HUD icons shows three missles)
-The Left, Up, and Right d pad buttons seem to do something (visible in the left bottom corner) probablly used for AA attacks, but they might be used for team communiation too or something.
-Most of the cars seem to have a passager to wield the sniper rifle/shotgun. How will this play out in single player? i doubt every character will have multiple drivers.
-Sweet tooth is again a traditional ice cream truck but retains a transformation (but can now walk instead of roll)
-Ambulance has a controllable special attack which u can steer. (looks like they took the design from Rogue Trip too)
-Looks like we know what those notes about dragging characters behind cars were about a few months ago
-Also the sweet tooth mushroom cloud looks like it was intended to be TM, since it's featured at the in home at the Twisted Metal E3 booth