Is it possible to inject USB signals (with power) through Ethernet?
I used to run USB and Ethernet in the same cable, to connect a router to a printer. I made two custom adapters to inject the 4 USB signals to the unused 2 pairs in 100Mb Ethernet. It worked very well, until an electric storm fried the USB port of the router; I don't know if the setup contributed to the failure. If you try it, make sure the USB data lines use a twisted pair, and 5V+GND use the other. In my case the distance was about 4 meters.

Edit about the failure: There was also a telephone line running next to the USB+Ethernet cable in the last 2 meters. Since the electrical storm also fried the ADSL modem, I think a voltage spike in the telephone line coupled into the USB wires and fried the port on the router.