Vegas doesn't care if BYU beats the spread or doesn't beat the spread. They don't care who wins or who loses.

The only thing Vegas cares about is making money, and they make money so long as equal money comes in on both sides. That's it. Once the game is on, they don't care about the result as the payout is going to be pretty much the same for them no matter which team wins/covers the spread. They take their same percentage of the bets either way.