if you're going to buy the audio subscription (Which, I will grant you will work for more games) you're almost better off buying the video subscription. This is the only other game (besides the NDSU game) that will be video cast, but hey video over audio = yes.
If you're looking for free.... yeeeeeeeeeeah usually one station will broadcast for free even though they aren't supposed to, but as for which one it is, you'll have to figure that out at kick off