You don't get any kind of formal contract with either Treason or Newsrevue. You can send the same stuff to either and they may both use the same sketch. Their audiences don't overlap, so it's not a problem.
As I understand it, you're agreeing to let them use your stuff in that current run, but you're free to send it elsewhere. It's all pretty informal. Topical comedy has a pretty short shelf-life, so you basically need to sell it wherever you can.