Usually, when an operation like BM&LP closes, like the Muskingum did a decade ago, it's cuz there's no coal left to dig
That's also what happened with BC Rail's Tumbler Ridge line with its unique GF6C's. Those were some of the first thyristor-controlled electrics, which IIRC allowed for efficient solid-state power conversion on high-voltage AC, vs. systems like the old CN commuter, which used a motor-generator set to produce 600vdc for the traction motors. The GF6C's were built on SD40-2 chassis with cowl carbodies, and I think one might have been preserved. The Tumbler Ridge operation lasted from about 1984 to 1998+/-, and shut down when the mine shut down.
Butte, Anaconda, and Pacific similarly shut down in the 1970's when the copper ran out. Kennecott Copper had an amazing rail system in the Bingham, UT, open-pit mine, all electrified, until the late 70's when they began dieselizing it with GP39-2's that had 12" (!) of clearance above the rail, thin fuel tanks, and REALLY tall cabs
Couldn't find any pictures of their electrics.
Oh well. Can't remember any more right now...