It will work provided you get a decent kit, not all ethernet over powerline systems are created equal. Netgear and Trendnet make decent solutions. BUT... running everything wireless is not a plug and play solution. You are much better off running wired ethernet but thats just my opinion. Once you get your network extended over to the barn, you really want to run cables anyways since you will have to provide power to the cameras. Since you are running cables you might as well run the one back to the house and simply avoid other issues. I would not run power over ethernet unless I had no other choice.I saw a you tube video of this and looks good and easy! If I understand correctly, it uses the existing electrical wiring of both house and shop as an antennae? I am coming out of my houses breaker box to the shop where there will be another breaker box. All off the same meter.
The better security cameras use what is known as PoE or Power over Ethernet. This simply means plugging in an extra small box (think smaller than a deck of cards) between the switch and each camera. This centralizes all of your power requirements to one spot. Alternatively you have to have power wherever you have a camera. PoE is easier and more reliable.
My security system runs PoE and I have a UPS plugged into PoE modules, this means my security system kkeeps running even if I lose main power.
If you have a generator, you may run into problems with powerline ethernet simply because most generators don't create clean power but you could get lucky.
Having things wired makes troubleshooting easy. With wireless its easy to run into problems that are hard to diagnose. I run wireless for my main connections because I don't have a choice (6-10 mile links). Once I get to either end, I run wired connections because I know everything will just work.