It's 40 miles. I would weigh the costs:
1. Terminate in MSP - means constructing a new service facility, leasing space from CP/BN/261, or operating out of trucks and trailers on a leased siding. Get the crews home.
2. Terminate in Big lake - means running extra 40 miles, fuel, crew, etc.. but purchase servicing and space from transit authority with ready-trained rail workers and mechanics. Get the crews home.
I think the real question is how far the crews can get from their change. Upon review of a crew map linked below, Winona is the easterly terminal. Crews are considered "away" there and work home, to St. Cloud. So the crews on that half of this new mini-builder (if the big one is Empire Builder, is this the Region Builder?) would have to proceed to St. Cloud after tying up in MSP or Big River. Given that crews have to go through Big River anyway, and there is already a service point there, it's a logical place.
Crew map: https://trn.trains.com/~/media/files/pd ... 0506_a.pdf