Also, just because they have access to coal, doesn't mean it's the correct grade to burn in a locomotive firebox. Oil as a fuel is MUCH easier to utilize, since the infrastructure of the steam era no longer exists. With oil, they can just drive a tanker up to the ROW and refuel. With coal, they'd most likely need to drag around several gondolas worth as part of the train, and also bring with them an excavator to transfer the coal from the gons to the tender. Oil just provides a level of flexibility that makes sense for the types of operations that the UP does with their steam program. Had they kept the 4014 a coal burner, it would never have left the Sherman Hill area, and we would never be able to see shots like the ones I was able to record from this last tour.