....I still don’t see how there wouldn’t be a criminal investigation to see who was at fault in an accident and I don’t just mean between the driver and train operator.
I assume you're referring to other accidents involving only the train or trains. The answer there is pretty simple. It's an industrial accident, and again, an internal matter. Unless of course there's damage or injury outside of the railroad, in which case the DOT would be involved. If the damage meets a certain dollar amount, the DOT may be involved regardless.
Local and state agencies have neither the authority nor the expertise to investigate railroad accidents.
Funny story. There was an incident in Weiser where one train collided with a car from another train, due to some operator error. All movement stopped of course, and soon there was a patrol car with two officers there. One officer boarded the locomotive and after being assured that there were no injuries and no hazmat leaks, he requested the crews IDs. The engineer politely explained that company policy stated that they were not to give up their personal info, and that a manager would soon be there and give him whatever was required.
Perplexed, the cop climbed off the train and didn't interact with the crew again. A few days later that engieer happened to be talking to the local railroad cop. The cinderdick told him that LEO had asked him, "who the hell does that guy think he is?" Cinderdick explained "the engineer was right - you were out of your lane."
