I can go either way on this. I've just playing the RAW. If the general consensus it to ignore the plus 1 on a road, well, I could easily go along with that. To me it isn't a big deal. As I see it, a unit paying the hill cost on a road could easily be trying to avoid silhouetting themselves on the ridge line.
2,500 years ago people worshiped cats. The cats have never forgotten this!