I don't claim to know Pittsburgh well enough to claim that this is a totally wrong idea, but the reasoning certainly seems to be wrong. Buses carry a lot more people than cars. People lining up for bus stops are, you know, potential customers. Maybe given the particular configuration of Pittsburgh's downtown there is a case to be made for getting the buses out of it, but I really don't think local businesses have the right idea if they think "unimpeded traffic flow for cars" is really going to be good for them. Also, too, it won't be unimpeded.