To me it sounds like 'make the corner rounded, smooth'
That might make sense if the sentence was:
The carpenter rounded the corners of the door
but I don't see how that would make any sense in the context of a train!
As what the phrase means, it could mean
The train went around the corner
in the case of a departing train, or
The train came around the corner
in the case of an inbound train.
As for whether or not this is a common usage or a rare/unusual usage, I think @Andrew was right on track about that. There's nothing unusual or jarring about it, especially in the context of a story. It's found elsewhere in literature, as in this excerpt (from the Simon & Schuster Survivors series):
She saw her mother reach out to steady her father, then the wagon rounded the corner and was gone, hidden by the pines.