Since any of the three will have no other losses to conference opponents. It will depend on the Strength of Conference Record. Oregon misses USC and ASU, Utah misses Washington and Cal, and UCLA misses Oregon St. and WSU. These two team pairs will be what to watch for because a combined Pac-12 record of each pair will determine who takes first (other pac-12 teams will have been played by all three members of the three team tie, so it will not help determine if Utah, UCLA, or Oregon has stronger Conference schedule). If Washington’s and Cal’s combined PAC-12 record is worse than the other two pairs of teams, Utah will get in because we missed those two teams and therefore our Conference Schedule will be tougher than Oregon’s and UCLA’s.
Once the first team is picked, it will be determined by head to head for second place. If UCLA takes first then we would have head to head over Oregon and would take second. So in the case of a three team tie with one loss each, we need to hope that USC and ASU doesn’t have the worse combined conference record as that would give Oregon first place and the Utes would be left out. It is pretty complicated.