Hmm thats actually tricky because of two main issues :
1- The example uses the C2 Car behavior which is 2 dimensional, the car goes on X and Y axis, so if you rotate the models 90 degrees on X axis, you will have problems with the car behavior, it will drive on the air.
2- The BabylonJS Camera has a fixed XYZ axis that cannot be changed, I can't make it to walk on the XZY axis.
I've got this request before in this thread about making FPS games from top down view C2 design, but I couldn't make it to work because of the engine limitations and the incompatibily with the C2 XY behaviors.
If you find any solution for this, please notify me.