Whether or not they can block services/ports/websites relies completely on your contract with said company. If you sign a user agreement when you start the service that gives them the right to block certain things, then they absolutely have every right to do so without fear of repercussions.
My home internet service is through my cell phone. I signed a contract with them that gives them the right to limit me if I take too much bandwidth. Its not a service that is meant for high bandwidth consumption.
Which is likely why they block things like speed tests.