What is with the untagged snowmobile tracks?

In recent weeks I have been editing OSM across eastern Finland. Everywhere I am finding ways tagged only snowmobile=yes that lack any highway= tag whatsoever. Often these ways overlap properly tagged highway= ways, causing JOSM to complain when I upload a changeset in which the proper highway= ways have been edited.

Where do these snowmobile=yes ways come from? Some mass import? Is any tool actually capable of using them as they are tagged?

I don’t know about the origin of these, and if there was an import which of those data sets was actually imported - the highways or the snowmobile objects, but I guess these snowmobile ways end up in this routable national snowmobile routes map even without those highway tags.

https://wiki.openstreetmap.org/wiki/Key:snowmobile

If there is no path nor anything else that should be tagged by highway tag then there should be no highway tag. Quite often it is simply a clearing through the forest marked to be used by snowmobiles or it could be on top of the ice on lake, like:
http://www.kittila.fi/sites/default/files/asiakirjat/KUVAT/A_sivujen_paakuvat/moottorikelkkareitit_kuva_levin_matkailu.jpg

I think most of the routes are imported from GPX-traces.

The problem with the current mapping, is that designated snowmobile tracks in Finland interact with the highway system, but this is not represented in the OSM data. For example, stop signs are often posted where a track meets a highway. Consequently, there should be at least an intersection node instead of just overlapping ways (as well as a highway=stop on the snowmobile track).

OK?

You are not allowed to ride a snowmobile on any highway. You are not allowed to drive a car on a snowmobile track. Intersection is not needed to allow routing between highway and snowmobile track, nor to anything else I can think of.

Stop sign is a sign. It does not need an intersection. All it needs is a node to attach to as a tag (key=value).