It's been a while since I watched it, but I recall my assumption being was that it WAS Holmes who hit the pavement, but he knew how to cushion his fall well enough to survive it. Watson (who was doctor enough to notice he was alive) was kept away (the bicyclist was probably an accomplice), Holmes had prepared lots of fake blood, and I didn't really think about the paramedics but it's not too hard to assume they were either set up by Holmes (possibly via Molly?) or he whispered something very persuasive while lying on the ground, along the lines of "pretend I'm dead and I'll explain once you get me inside."