UPDATE: I've uploaded the executables for the Bullet physics test and the new scene with the soccer playing field at http://code.google.com/p/tokap-the-once-known-as-pong/downloads/list
I've recreated the truck from 'Unbiased Truck Soccer' in the Bullet Physics engine and applied some physical properties to make it behave like a real vehicle like suspension stiffness, damping, rolling and friction.
This is a video of what the gameplay should be like when using the Bullet Physics engine, made with the built-in debug OpenGL renderer of Bullet:
And a Soccer game is not complete without a huge open playing field. The goals will be represented by a blue and a red sphere. Players can score by bumping the soccer ball against the opponent's sphere.
The hardest part is using the output of the Bullet Physics engine to update the position of the trucks and the soccer ball in the real-time path tracer. It should be fairly straightforward though, so I hope to have a working version soon!