The idea to put datacaps on a freaking internet landline is beyond degenerate and evil, that kind of sinister crap would never be allowed in Sweden.
I haven't heard of land line data caps being forbidden in any way, but it presently wouldn't work here in Sweden because there is a lot of real competition in most places. That could well change over time in rural areas, as DSL capable copper is being nibbled away and "replaced" by 3G, but there's a lot of "open" fiber going to just about any smaller town.