The norm is that in-state tuition depends on where parents live (and pay taxes).
Some states, like Missouri and Utah, make it possible for a student to apply for in-state tuition if they live in the state year round;it also typically requires registering to vote as well as registering a car. Those are known to be especially generous.
You can ask Montana but don’t expect much. The main points of bringing Oos students are geographic diversity (so the campus can represent some of what the country is, not just a little corner of it - for that purpose, Montana State is part of WUE) and Oos tuition (to offset budget cuts).