They’d be stupid not to watch television for updates.
That would be an interesting trick if they turned off the electricity to the place.... Most terrorists aren’t going to be smart enough to bring along a battery powered TV or a long-life laptop.
They might be receiving intel from outside the building, but then, if they had someone outside watching in person, the TV isn’t going to matter anyway. Remember, when the SAS raided that embassy in London, the TV cameras were watching and it didn’t matter then either.