There is a market for old tools, period, and there is a market for railroad tools that are marked for a particular road, and with the Q being a fallen flag for several decades, yes there would be some value. If it is clearly a steam era wrench - meaning, that it is huge - that could add to the value although I suppose it also means that you lose the market for someone who just wants a good wrench around the house. My experience is that there is less collector interest in tools than in lanterns, glass, china, silverplate, and paper.
I cannot begin to guess value but I have paid $50 for a very old Chicago Milwaukee & St Paul (it leaves off the "& Pacific" so it is clearly old) tool.
This site seems to be a common ground for folks in the railroad relics business
http://www.railroadiana.org/
If you have never been to a railroadiana show you might find it interesting and entertaining. It is a whole 'nother bunch of folks than go to model train shows.
http://www.railroadiana.org/pgCalendar.php
Dave Nelson