Certainly there are valid considerations for infrastructure design and regulations regarding where hailing can be conducted, but if it's okay for a customer to

Certainly there are valid considerations for infrastructure design and regulations regarding where hailing can be conducted, but if it's okay for a customer to hail a cab from Company A at particular location, I don't see a valid reason for not allowing Uber to do the same. I find your color argument unconvincing, but even if it were valid, I'm sure Uber and their drivers would be open to putting identification on their cars if it granted them access to desirable customers. Additionally, it's not as if increased competition among firms who can respond to a hailing customer will inherently increase congestion due to street hailing. This would only be true if existing companies were (a) underserving the market so significantly that the ability to hail additional cabs from the curb allowed previously unmet demand to be satisfied, or (b) demand for street hailing itself were to increase. I think (a) is possible, though unlikely, because hailing from an app is generally more convenient than standing on a curb and flagging down cabs. I think the same would apply for (b). If anything, companies like Uber provide a way to more safely and efficiently pick up passengers without relying on street hailing.