From what I can find online, there's not a lot of precedent for penalizing the home football game for fan interference. Game is simply delayed, then continued. Artificial noise makers is one penalty that was called in the past, but I couldn't find any case where storming the field was penalized. The team is penalized, however, every time fans storm the field... and the penalty amount escalates with each occurence. SEC recently doubled their fines, so they're really trying to crack down. Fun fact: if you do it after an NFL game, you lose your season tickets and are receive a lifetime ban for the stadium (wow!).

In the BYU/ASU case, it's a pretty weak argument anyways because the clock hit 0:00. Of course the fans are going to think the game is over.