This is a classic case of a politician saying something, anything, to get his name in the local paper. The (State) Senator offered no reason that BNSF should reopen the line.
The only reason would be to handle through traffic. BNSF already has access to Butte, which is a mere shadow of itself in terms of local traffic.
Homestake is obviously BNSF's third choice of routes across Montana. The common points are Laurel, near Billings, and Sandpoint Idaho. Laurel to Sandpoint via Helena is the former NP main line now operated by Montana Rail Link under lease. BNSF is obligated by contract to give MRL a certain amount of traffic. This route is the natural route between the Pacific Northwest and former CBQ territory, except Chicago.
The BNSF's favorite route is the former GN via Havre to Chicago. It has only one mountain crossing and its grades, and thus operating costs, are lower than MRL which has two widely separated steep grades in each direction. The GN is congested in North Dakota due to the oil boom but BNSF spent about $500 million on capacity improvements in 2014 and will do about the same in 2015 because this is THE low cost route across Montana.
BNSF also has a line between Laurel and Shelby via Great Falls. This line gives BNSF the ability to route traffic via either MRL or its own line. In GN days this was a 1-2 pair of thruough trains branch line, but I understand that it has been improved since.
On a micro level, Homestake is an alternative to Mullen Pass which is MRL's active route. Mullen is no prize with a longish 2.2% grade ascending westward. IIRC eastward grade is not as steep.
Homestake is 2.2% both ways. As long as traffic does not overwhelm Mullen there is no reason to mess with Homestake. Traffic is very unlikely to overwhelm Mullen because BNSF can route around it all on own rails and MRL could expand capacity over Mullen. If I were a betting man, I would bet BNSF will route increased PNW - Laurel traffic over its own line via Great Falls.
Why would anyone even think about reopening Homestake?
Mac McCulloch
