I think it largely depends on both the client and the company. Though, I'm guessing a TV station is a bit different than a studio in that regard. Like some work I did for Farmer's Insurance.. I'm not allowed to put any of that in my portfolio, for some legal reasons that are beyond my control. In fact, MudBrick isn't allow to put any of that work on the company website as we got the job through the local university who hired us to do the work :P. Weird situation, but I definitely do not have any rights there. Would be nice, but oh well.
Then I've had other situations where I was working on a project but the client requested that I not share any of it (not even partial shots) until the project was published/released. Not so sure about project files though. I've shared some in the past, but not sure if that was even allowed :P
It looks like you're new here. If you want to get involved, click one of these buttons!