and found
almost 20k spots where this was the case; while there were some false
positives (bridge or railway maintenance buildings), in most cases the
railways seemed to have been completely built-over with no trace
remaining except in the heads of those who used to live there when there
still was a railway.
I looked at a few of these hits you provided and often it was clear from just looking at the map where the railway had been, because of current features like road layout, tree rows and similar, also names, and even if there were some spots where the former line was intersecting with buildings. In the German discussion we spoke about railways completely built over by residential quarters or a supermarket but in the map you provided it was much more often the case that these intersections of longer lines were at a few spots while generally they were not overbuilt.
Also former tramways in cities are often cited as abuse (and I tend to agree), but these are very different from heavy railways outside built up areas, and it is less likely to find traces of former trams on the current surface. Usually there weren’t tunnels or embankments built just for trams, they had much fewer impact on the landscape.