I'm just guessing, but if they really own it, they can screw Warner by blocking the release, effectively causing Warner to lose everything they spent on it (as in, they spent a few hundred million and won't make a dime of it back).
They'll probably aim to get all of the profits, not a slice. If they do that, Warner's only option will be to appeal the ruling, or to potentially break even at best, while watching hundreds of millions of dollars in profit go to FOX for nothing.
It could get very nasty.