If BYU managed to finish in the the top 6 of the final BCS standings, they would have gotten an automatic invite.

"BYU can become eligible for a BCS bowl if it finishes in the top 12. It can earn a guaranteed BCS bowl berth if it finishes in the top six. Should the Cougars be invited to a BCS bowl, the Fiesta Bowl, held on Jan. 1, in Tempe, Ariz., is the most likely destination."
http://www.deseretnews.com/article/874192/BYU-doesnt-budge-in-BCS.html

Those were the same requirements Utah had to meet in 2004:

"A top-six finish in the BCS standings guarantees a spot in either the Orange, Fiesta, Rose or Sugar bowls, each with payouts of over $14 million. To even be considered for a BCS bid, a top-12 finish is required."
http://www.deseretnews.com/article/595100899/Sooners-Utes-jump-ahead-in-BCS-rankings.html