Tesla seems to have a mixture of data for driving and potentially a different primary source for each of road connectivity vs speed limits vs lane data -- and maybe even depending on the region. Tesla can of course augment it with their own fleet data collection. From digging into problems in FSD Beta videos from before, a lot of lane selection issues matched up very well with OSM having wrong/missing lane counts and turn lane information. At least from my testing so far, it seems likely OSM is not the source of speed limit data, but I'm not sure what services provides (free) access to their speed limit data remotely.Not sure Tesla uses OSM for anything other than summon
I did find another road that does not have OSM maxspeed data, and the car switched to 20mph before seeing a sign and then visualized it!
I wonder if Tesla knows their under-25mph sign detection is not as confident, so they currently require map data to confirm before showing? But at least we know it's possible for both 15mph and 20mph signs to be visualized now.