If they stopped the train in a subway under a major city, they would have so much extra energy to put into grow-lighting they could feed everyone fresh food every day.
They’d stop. They’d sew together the best Arctic suits they could. They’d send out scavengers to get equipment and bring it back.
And gradually they’d build a comfortable colony in the subway, with everyone on a good enough lifestyle to stop revolutions because we’re talking about the fate of the human race here.
So STOP THE TRAIN YOU FOOLS!
Sorry, but really bad Sci-Fi presuppositions bug me. I had to rant about it over on Reddit.