We owned a flat with a communal dish, everything was as normal, we just shared the dish that's all. Each flat had 2 coax sockets for it with at least 1 actually connected (i went into the cupboard where the equipment was and hooked up the second one that was disconnected mwahahahaa).
Didn't have to sign up to sky, could have Virgin media if required.
Phone was all the same, each flat had it's own separate master socket, changed providers as per normal.
However, this was my experience, it depends who built the place and how it's cabled. Definitely check all this before you sign anything.