We were on the Vista last year around this time and the Skybox Sports Bar had ESPN, ESPN2, ESPNU, and the SEC Network. We wanted to watch playoff basketball on TNT and playoff hockey at the time on ABC. We were told that Carnival only paid for those 4 ESPN owned channels and that was all they could show.
Now with saying that. I have seen Carnival do special broadcasts of NFL games. The ones I remember from last year where on a Thanksgiving cruise on the Breeze and they had two of the Thanksgiving games on the big screen on the LIDO deck. They had signs up letting people know the start times of the games. Cowboys game was shown.
We were off the boat before the Sunday games, so I have no idea if those were shown.
So Carnival could theoretically show games but if they choose to do so on a certain cruise is up to them.