As I read it, it's not paint, it's actually mixed into the concrete.

As far as whether it is effective or not... well, it's probably more effective than not doing anything (additional costs and construction techniques need to be considered). Overall, I think absorbing pollution near the vehicles that produce it is a good idea. The raw amount of paved area in the world makes it an attractive target for any 'green' development (I've heard of projects trying to put solar panels into roads).