Yeah this is something I've been looking into for a while actually. There's a cluster of sightings along the old Crouch Valley line in Essex that nobody really talks about, and when I mapped them out they follow the route almost perfectly. Old railway cuttings make sense as travel corridors - dark, overgrown, not many people, often running through woodland that's been left alone for decades.
The thing that gets me is whether the railway came first or whether these routes were already something, ley lines or old drovers paths or whatever, and the Victorians just built the tracks along routes that already had... significance. Dogman reports in the US also cluster around old rail infrastructure, theres a researcher in Michigan whos been documenting this for years.
Anyone else been out mapping this stuff? Would be well up for comparing notes if people have UK sighting data they want to share.