I bet your association gave them permission to do this. You need to take this up with them. If you're in a townhouse or condo, they own the outside walls of your home, and the land around it.

They can do whatever they want with it then. I"m not sure if they can do this with an actual 'house'. I bet Comcast has a contract with your association or town even, and has eminent domain to cable in your area.