I'm not sure what to think about Fox. Fox did re-up on MLS - even with the Apple deal. MLS is producing the broadcasts for Apple TV with a GOTW also shown on Fox (different announcing crews). So maybe, Fox may be involved in a similar way for the Pac-12. In any case, I'm on record predicting the Pac-12 deal will be close enough to the Big 12/ACC deals.
I think a sublicense deal is always possible for Fox or anyone.