I have to assume that USU and the other schools expected some kind of retribution from the MWC and factored that cost into their decision to leave.

I don't know enough about the MWC's bylaws to have an opinion on the technical merits of this complaint, but some of the concerns and arguments strike me as... not very strong (of course the exit fees are supposed to enrich the remaining schools, that's the entire point; of course USU and CSU leaving early causes harm, in the tens of millions of dollars, to the MWC)

I also consider it very telling that the other exiting schools haven't filed suit.

I'm pulling for USU and CSU here (both as an Aggie fan and because the MWC sucks) but I'm thinking that the MWC has the stronger argument.