Assuming that the particular link functions reliably, and given, as Kijanki indicated, that sound quality is not influenced by link timing, the main question that arises in my mind is not interference TO the device, but interference FROM the device(s). In other words, whether or not the signals that are introduced into the power line by the ethernet-to-power line adapters, that will to some degree find their way through the power wiring into the audio system components, would have audibly significant effects on those components.
I have no feel for the likelihood of that being an issue, and that likelihood, if any, would certainly figure to be dependent on the design of the particular components that are involved. But assuming that the link functions reliably, that is the main question IMO.
Regards,
-- Al