Never looked into dogman much but this is actually interesting because the railroad correlation keeps coming up and nobody seems to have a decent theory for why.
My gut says its something to do with the land itself rather than the trains. Old rail lines in the UK and probably the US too follow older paths - drovers roads, ley lines, whatever you want to call them. The rail companies didn't just pick routes randomly, they followed the terrain and often the oldest routes through an area.
So maybe the dogman isn't attracted to railroads specifically. Maybe both things are in the same places for the same underlying reason, if that makes sense.
Anyone got actual sighting reports with coordinates or rough locations they can share? Would be good to plot them and see if theres a pattern worth taking seriously rather than just going on anecdote.