Supercoupe - am I right in understanding your issue that the POE cameras are not powering up via the Powerline connection (12v DC camera power)? If yes this will not work as all the powerline is doing is converting the TCP packets to transport across the wire, not the DC across the AC connection.
You would have to use a 12v power supply at each camera location to power the camera unit. You can get the video to travel via the Powerline transport but our experience has seen issues when trying to run 1080p successfully on more than 2 cameras in the same structure (same building, same electrical service)
One install we have that the customer wanted only Powerline to be used rather than the expense of running new Cat5e loses video to all his cameras when the air conditioners kick on (data via PL on BNC "HD" system)
Lorex's suggestion to use wireless is probably the best although like "death from firing squad or death from hanging" either one you die...run some Cat5 connections to the cameras