Below are updated probabilities of final Big 12 standings. BYU solidly in first and Colorado now slightly ahead of Iowa State for second.
BYU ends at least tied for 1st 83% of the time. Wow! They definitely get to championship game 74% of the time, and 20% of the time they would be in position to go and it would come down to tiebreakers. Only 6% of the time do they end in 3rd or worse and guarantee they won't participate in the championship game.
Overall for the conference, most likely that the 2nd place team(s) have 7 wins, 2 losses. A reasonable chance also that top two teams have 1 loss or less. And slight chance 2nd place team could have 3 losses.
If BYU can win on Saturday - they would have a 92% chance of finishing alone or tied for first. Just keep winning!