Doesn't sound crazy at all, there's not really anything in your breaker panel or your meter or the outside wiring designed to stop these signals, it's just that there's also nothing designed to help the signals make it through all that, so you wouldn't expect it to continue beyond your house. Just like they tend not to work very well when used on different circuits, they shouldn't work very well outside your house, which is certainly not on the same breaker at all.

I think the newer ones all have some sort of encryption/pairing system which at least helps you ignore your neighbors transmissions.

There are phase bridges to ensure powerline signals are on both phases in the typical US house, and phase filters available that filter the powerline frequencies - they were originally conceived not so much for leaking out, but preventing noise from leaking in and interfering with powerline stuff.

X10 users have used them for years - you can find them with vendors that specialize in dealing with the X10 community or home automation; although with the wireless mesh networks like Zwave or Zigbee a lot of the powerline stuff has (thankfully) fallen by the wayside.

Another way to get wired internet without possibly running new cable is with MOCA - ethernet over coax. You can find cheap DirecTV branded MOCA adapters all over the place. Most are 100Mbps but if you watch the newer ones are gigabit capable.

Ethernet over coax? That’s some OG networking. Break out those 10base5 adapters from ur possibles box. I guess this is also the time to bring up the obligatory Ethernet over barbed wire solution: http://www.sigcon.com/Pubs/edn/SoGoodBarbedWire.htm

They're talking about MoCA, multimedia over coax. The standard is from 2006 and runs over regular household rg59 or rg6 coax.

That being said, I've worked with 10base5. Drilling for a vampire tap in an open elevator shaft is its own form of exciting.

Personally, I've had much better luck with MOCA than with powerline. Full gigabit speeds in an older 1940s house using basic Motorola adapters off of Amazon.

Same. Plugged in the device-side one of a pair and the device started working before I plugged in the router-side one. It'd connected to a house two or three doors down.