Powerline adapters are pretty cheap nowadays and fast enough. I get synchronous 200mbps over a pair of TP-Link gigabit ones in a place with really poor quality wiring, and they come with power pass-through so I don't even lose a power socket.
I do use a powerline adapter and it works but I'm afraid that there aren't too many eyes looking at them - what if they have a big flaw and it stays dark?
There's no way these adaptors aren't vulnerable, given the nature of them. In my opinion. Extracting the signal from the mains and feeding it into GNU Radio for demodulation, then subsequent attack, would be an interesting exercise.