Yes, it's a transit road, a private road but not a "Landesstraße B".
Is it signed as such? ownership doesn't matter as much as signage.
I never drove the road and GSV is not available there. I couldn't find any pics on wikipedia showing a sign but the article says that there's an internal number "P1" which is sometimes used, e.g. in news articles. B108 is indicated on GM but not on OSM or BM. GM does not indicate B107 and B188 which are similar routes like I've mentioned before.
Si is the 'master of desaster' for Europe. I'll wait for a response from him but any opinion is welcomed.
Disaster?
Germans sometimes say: "Er ist der 'master of desaster'!" ("He is the 'master of desaster' !). It means that the person is responsible or should be involved to any discussion about this issue. It sounds negative but it isn't.
btw: Maybe a provinicial roads tier 5 system like cansph?
cansph is a tier 4 system that its European equivalent would be a system with a few tier 4 roads from several countries. I debated doing something similar and had TM started a couple of years earlier there would have been this.
A tier 5 system 'Select other European roads' (eursor)? What roads are you thinking of adding? I've got a handful of short GB ones (non-tourist routes).
I think about my favorite topic "ugly gaps". Roads which are tier 4 till the border but the continous road of the neighboring country has a lower classification while it has the same importance. There are many b/n DEU/AUT, AUT/CHE, CHE/FRA, DEU/AUT,... Or gaps b/n tier 1 and tier 4 routes which are do not fulfil eursf standard.
I'd prefer
eursor but
eurap (Alps passes) could be mapped completely because there's a reference list (see my links above) and less discussion.
Edit: I forgot the most important "gaps", the alps passes mentioned above and roads like St2622 north of Passau (
http://www.openstreetmap.org/?lat=48.688467&lon=13.423233), St2580 Flughafentangente Ost (
http://www.openstreetmap.org/?lat=48.335399&lon=11.866136), L76 south of Berlin (
http://www.openstreetmap.org/?lat=52.367424&lon=13.402977) which closes the gap b/n eursf L40 and B96a or Autobahnzubringer Backnang (
http://www.openstreetmap.org/?lat=48.982477&lon=9.325751). I don't think about former German B roads et cetera
.