The bus span because the driver had seen him and tried to avoid him. You can see the spin starting before impact.
I'd guess that the back wheels remained locked throughout, so he didn't go under them but was just dragged along the wet road.
A lucky chappie.
There are a number of things here that scream 'Fake' to me! The cyclist - when we first see him, dark clothing, dark bike; when he emerges from under the bus he pulls something light down from the underside then rolls over and plays dead - could it be some type of padding? The white MPV driver - if you see a huge bus coming towards you would you a) calmly put your hazard flashers on or slam it into reverse and put your foot down? The pedestrian with the umbrella - acting too calmly, he looks as if he is waiting for it to happen.
I agree with Andy, people when presented with a shock situation react in all manner of bizzare ways. As for the cyclist jumping up and then rolling over and playing dead - haven't you ever hurt yourself, tried to get up and then given up to the pain and got back down again?
The usual reaction to any accident in China is calm and dispassionate. What's unusual about the reactions is that no one was rushing to the scene with their camera phones in the hope of getting as many gory pictures as possible as a man bled to death.
I must say I wondered about the ped with the umbrella who didn't seem to be legging it as fast as I would, but it's hard to account for the actual situation and people's reactions without being there... Shock does funny things to people and people's reactions differ...
something similar(ish) happened to me as a youngster - although the lorry was stationary at the time me and my friend who was giving me a backie down a V V steep hill onto the road junction went right through under between the wheels and out onto the main road on the other side. Bloody hurt though.