There is a good article on Grantland.com called The Curious Case of Mark Buehrle.
Good read, track it down.
I think Buehrle proves a couple of things.
He is the exception to the rules…well, several rules. Soft tossing control pitchers usually get figured out pretty quickly in the pros, he has not.
He has had a long run of success despite not throwing hard and not striking guys out.
So, low velocity, lots of contact, low strike outs…he has something else working.
I would suspect that while he may not have big movement on pitches I would be willing to bet he has late movement on almost all of his pitches. Enough movement late enough in the flight of the ball to not cause a ton of swings and misses but to generate relatively weak contact.
Just a guess.