It is not exactly common knowledge that sub zero temperatures affects roads. The general public don't think about water under the road and it's effects when it freezes. They only think about ice on top of the road. I only know because I am a documentary and former weather channel geek.
Here there are problems getting potholes seen to. It is a local responsibility. So councils in northern communities need to find and dedicate more funds to keeping the roads up than do the southern communities. I think the BBC explanation is geared to helping readers understand why more council tax must be dedicated to highways maintenance.
The title of the article is a bit unfortunate and kind of dumbed down. The research would have been required but it need not have been so obivious.