I don't see how that law comes into effect in this situation unless they left something out of the article. It didn't say Tesla is preventing others from opening services centers, just that Tesla owns them all so far.

There's probably a non-trivial amount of model specific knowledge needed to repair a Tesla that can't be picked up at a general mechanics' school. Maybe when Tesla's sales volume increases there will be a higher demand for mechanics that Tesla couldn't fill and 3rd party shops will open.