My company, RealSpace, has recently produced a simulation for Teck, to help train their vehicle operators on safety hazards. We used Bullet to power our vehicles and collisions.
The vehicle that operators are training on is a rubber-tired bulldozer: a 50,000 kg vehicle with fixed axis wheels and a two-part hinged chassis. We implemented it using two raycast vehicles, and a hinge constraint, and although we had to up the maximum suspension forces a little, Bullet was able to handle it extremely well.
You can read more, or see a video of the vehicle in action here.
I'd also like to thank everyone on the forums here who has answered my questions in the last year or so!