That's frightening.
No, that's just silly. People can always go down and listen to their car radio. Not to mention that such a dirty bomb is designed to create panic, so why would they want to knock out the media?
Odds are very strong that this (like so many other previous incidents) has nothing to do with terrorism. But if it does, the power outage is probably an ends to itself, to scare. Which would also suggest that this the best that they can do.