Ethernet Power Line Adapters

[HSD <HSD@xxxxxxxxxx>]

I am looking for information on Ethernet power line adapters.  In
particular, I am curious if anyone has had trouble with them working
across the two legs of a 120/240 VAC system, as sometimes occurs with
X10 systems?  At the other extreme, has there ever been an incident
where a second residence has been able to access the network of the
first residence because they were attached to the same pole transformer
secondary?

If this is the wrong group to post this in, my apologies, but it seems
that people that understand X10 problems, and also used Ethernet power
line adapters, would also have a good feel for the performance of
Ethernet power line adapters and their weaknesses