Be careful! If you have to do a big change to the map and you're really far into detailing, it's going to be very difficult to motivate yourself to delete and redo all that work!
If detailing (like the train) is part of the gameplay of the level(ie, can kill players, block sight lines) then I'd say it's more than okay.
Its outside the map. I was bored and wanted to start looking at scaling.