it doesn't support IEEE 802.3af standard PoE. but PoE is the CONCEPT of running the voltage over the unused (Or overvolting the USED dc wires) on the Cat5 cable. (blue and brown/blue+white and brown+white). and the Raspberry pi CAN be modified to do this...

I imagine it can be wired over cat5/cat6. but need to make sure after the dc is taken to power the pi that your not overvolting the rj45

(3.3v actually I think for rasberry) - and for PoE, you can use blue wires or green depending on 568-a or B wiring. (IEEE 802.3af is DC+ on pins 4,5 and DC- on 7,8)