I don't see the Montana schools leaving the Big Sky for anything less than an FBS invitation and I absolutely don't see Montana State-Billings jumping up. MSU Billings is tiny, poorly funded, and largely irrelevant even on the local level. It's the only DII program in the state, but it's below NAIA Carroll & Montana Tech on a pecking order where only the top 2 programs are anything approaching D1 size/scope. Montana is a one sport state (football) and Billings doesn't have a team in that sport...that kinda says it all. I don't want to be too harsh on them (being in Billings is harsh enough), but it's just your standard small, public DII branch campus with neither the money nor ambition to move up. Survival is tough enough.
From a UM standpoint I
really don't see the upside in such a move. That's a worse conference than the Big Sky in every way. Maybe it's that I'm overly-oblivious to basketball (Grand Canyon has a campus?), but so is Montana in general. Both UM & MSU make decently regular trips to the NCAA Tournament, so it's not as if the Big Sky is holding them back. All the UAC would add is higher travel costs for lesser competition.
Northern Colorado could probably be swayed by the idea of being something other than a doormat; their jump up from DII power to Big Sky cupcake has been excruciating to watch, but Montana & Montana State lack a reason to consider such a move.
On a related note...this Saturday's (4) UC Davis @ (7) Montana game will be on ESPN2 to help underline my point