It's not what the powerline adaptors are doing for you, DtG, it's more what they're spraying over the environment while they're doing it. Even the best-designed wired networks will leak (the trade keyword is TEMPEST*), and house wiring is not designed as a computer network.

I'll save you the coredump on our radioastronomical Project's adventures with avoiding interference from a stray overtone emitted by the campus network. Trust me: that saga has the "How are you?" --- "How long have you got?" nature.

* An acronym, as well as a cuss-word.