At least from my recollection, commercial rail has an incredibly high amount of regulation and union involvement.
Which means a minimum 2 person onboard requirement.
I can’t imagine it being an easy market to break into, despite all the technology being there.
Wabtec, the locomotive giant, today has TripOptimizer which is smart cruise control, which might be all you really need for most situations.
Barring release of sand and operation in the rail yard.