Life Imitates Art Imitating Life
Reports emerging from the investigation indicate that the driver had not properly set the brakes before exiting the car, and further had tied off the “dead man” lever that controls the train’s movements. (This has not yet been officially confirmed, so we’re going here by reports from The Boston Globe.)
This could be a remarkable instance of life imitating art, said art having already imitated life.
That movie, in turn, was inspired by a real-life incident in which a freight train in Ohio, carrying dangerous cargo, rumbled along without anyone in the cab for 66 miles before finally being brought under control in much the same way as in Unstoppable.
It would be very hard to make this stuff up and have anyone believe you.
*In the film, the engineer was clearly a dunderhead. I'm not suggesting that the driver of the T train was. That's for the investigation to decide.