Two quick stories about railroad work clothes. When he was growing up, my father had a neighbor who always left for work in a suit and tie, carrying a leather bag. My dad always assumed he was a doctor, until one day he was at North Broad Street Station in Philadelphia, and a train came in with his neighbor at the throttle in a full herringbone boiler suit. My wife's grandfather was an engineer on the Pennsylvania Railroad, and he always wore a full boiler suit and a necktie. On the big railroads, there were locker rooms for the train crews, and I'm fairly sure they wore different clothes to and from work than what they wore on the job.
But -- if you look at the photos in TFTT and the other Maine two-footer books, you'll see that the crews wore whatever they had as work clothes. I do recall one photo showing the RPO clerk on the WW&F wearing a long-sleeve shirt with a tie. I imagine our local fellows wore the same clothes all day, without a change. I think as long as our train crews do not wear AC/DC T-shirts or Red Sox ball caps turned backwards, we're okay!