Since not all 3 teams in the 3-way tie-breaker played each other, it would advance down the different criteria until criteria d, which is conference SOS. KSU currently has the edge on ISU in this scenario and would likely move on from the 3-way tie. BYU has no chance on SOS.
After either KSU or ISU moves on, it moves to a 2-way tiebreaker between the 2 teams. If it is KSU-BYU then BYU wins due to H2H. More likely it would be ISU-BYU since KSU would have already moved on. For ISU-BYU it would move on to tiebreaker criteria c, which is where CB is divided on the interpretation.
Criteria c says “The tied teams will be compared based on win percentage against the next highest-placed common opponent in the standings (based on the record in all games played within the conference) proceeding through the standings.”
The question is whether “the next highest-placed common opponent” is KSU (in which case BYU would win) or if it would be the “next” team down in the standings since KSU is not the “next” team.
Note there are a couple other ways the 3-way tiebreaker could be resolved depending on who BYU loses to but it won’t affect the final result.