I do think the plan for the Big XII is to take the Arizona schools, UU, CU and then force UO, UW's hand.
However, we don't need CU, UU to get UO, UW IMO. The B1G may not ever take UO, UW so those schools would have no choice but to move to the Big XII if the Arizona schools are gone. Short story, we can get UO, UW without CU, UU if we play our cards right.