No. Powerline ethernet was pretty obviously going to have security issues along these lines from the go considering the lack of clear boundaries inherent in sending data over wires connecting to a public grid and included cryptography from the go. I know Homeplug devices have been on AES since the mid-2000s using either passwords or push button config and G.hn had something similar going on.
To elaborate, the power conditioning circuits in flat screen (often plasma) TVs would interfere with the non-60hz signaling of the powerline ethernet. That's certainly not the same as breaking into the network, but it may have been enough to knock devices offline.
