I do not believe the networking will pass through the main breaker. I know for a fact it does not for Ethernet over power line
The main breaker does not block the signal. The first transformer blocks the signal - IF it is an older style transformer.
All new electric transformers are being built to pass internet over power lines [IP over power line] so the electric utilities can read their digital meters via either a wireless [cellular] or powerline-internet connection.
Additionally, if you live in one of the areas served by Excelon, the parent company of Commonwealth Edison of Illinois, you are probably no longer on a single-transformer feed. Because of all of the new power demands in homes, caused by large screen televisions and computers, ComEd, Excelon, and many other electricity distribution companies, are going to bonded transformer setups. In a bonded setup, they no longer feed 1 to 6 homes off a single transformer, but, where the density exists, and the feeder lines are short enough, and heavy enough, to prevent significant voltage drops [20% of all the electricity generated is lost to heat dissipation because most of the distribution wiring is undersized for today's loads], will segregate the single phase 220 / 240 volt residential and non-three phase feeds into a feeder cable that is fed by up to 10 transformers over a multi-block area.
This provides several advantages for the electric utility:
- An amperage demand reserve in the case of a sudden demand by one or two customers in the same area;
- A safety net in the event that a transformer craps - the former 5 to 6 homes or businesses which might have been on a single transformer and lost power altogether will not be in the dark now and can draw from the shared transformers which comprise the remainder of the bonded feed; and, finally,
- Greater control over the regulation of the voltage to the customer because the transformers act as a pseudo capacitor bank and can absorb sudden demand requirements of one or two customers who suddenly switch in a high load simultaneously - as in a situation where it suddenly gets extremely cold and a group of customers with electric heat all call for heat in close proximity to each other.
So, don't count on an IP-over-power line data signal not being transmitted to, or received from, a neighbor down the street. If anything, as the new technology for IP-over-power lines becomes more installed, you will have to worry about that much more than you do now.
What you can do now, which will also take care of the future, is invest in a whole-house surge protector. These can be found, relatively inexpensively, on eBay. You can also find whole house data repeaters which attach via a 220, double poll breaker, and regenerate the data transmitted on any phase in the panel to the other phase to make certain it is not blocked to a particular outlet which is "on the other side" of the 110 phase from the one you are using in a 220 volt, single phase household or business.
