A modern freight train needs an engineer and a conductor to operate. Mile-long trains are the general rule. I could see the point of using two people to operate a THREE-MILE-LONG train instead of three separate trains but it sounds like the challenges are greatly multiplied by such length.
I have delivered railroad crews to BNSF trains in an SUV. Sometimes I had to drive one of the crew to the other end of the train which was a mile away, then wait, and bring the crew member back.
Operating a passenger vehicle in a busy railyard is dangerous and requires great caution and vigilance.
I have a vintage PRR rule book.
That sort of thing would NEVER have been permitted back in the day!