disused:railway=rail seems to be quite common.
I’ll show it to my map with the next update.
But tracktype=grade4 and smoothness=bad don’t sound a like a nice railtrail for everybody. Not sure I’ll want to cycle there with my road bike… Rather take the MTB 
Maybe I should show it in a different way than “good” railtrails. Any suggestions?
The route seems to be quite spectacular, though!
Btw, my plan is to setup a dedicated domain in april and then announce the map to a broader audience, including the english language forum.