Remember that BNSF made a car haulage agreement with UP for traffic off the StMRR via UP's Plummer-Spokane branch right after the '97 floods washed out portions of the WI&M. If clay from the Helmer fields is bound for Helena, it'd probaby move over the StMRR to Plummer, UP from Plummer to Spokane, then BNSF/MRL to Helena.

I just don't see any rationale for the WI&M to be rebuilt between Bovill and Harvard. It doesn't follow the regional commodity flow primary direction, e.g. the WI&M runs along a line drawn roughly SE to NW, while most local commodities flow south/southwest. Of course, once the local commodities leave the boundaries of the inland region, they go primarily West (Asian export trade) and South (the California markets), with some heading East. Hardly anything will be headed North, NW, or NE relative to the geographic position of the region.