You can download the mod itself here (at the very bottom).
Added 22 hours 25 minutes later
Okay, I archived the "C4M3" extracted from data.pak as an h5m file, opened it with an editor, and... there are no roads! This explains a lot. But the most interesting thing is that if you use the original extended editor to go to Open Resource, open AdvMapDesc, and then select and open "C4M3", the map version with all the roads will open! Conclusion: the normal map is not stored in data.pak, but if not, then where? I tried using versions of the same map from "p0-data", "p1-data", and so on, but they also don't have roads, apparently. By the way, what are these duplicate archives for, are they patches or something?
Added 1 hour 47 minutes later
Suddenly, it turned out that the problem is not with the map at all! The problem is that you cannot lay a road on the "subterrain" terrain type. It seems that a conflict occurs during map processing, and because of this, the road "blurs out". In any case, if you change the terrain type in the editor where the road should be, it appears.