I doubt that you can do that. The DC socket almost certainly has some regulation circuitry on it and you can't drive that in reverse.
Assuming that the 24VDC source has sufficient current to drive both the RB433 and the camera, your best bet is probably to make up a custom CAT5 splitter to extract the power before it reaches the RB and inject the data output from the RB.
If the camera is entirely passive you should be OK, but if it contains motors for focus, tilt and zoom you may get problems with back EMFs causing interference to the RB. It really depends on how good the regulation circuity is on the camera and RB. It's certainly worth a try on a test bench and if you get problems you may need to look into getting an active power splitter.
The power will be on the Blue and Brown pairs on the CAT5 cable. The easiest way to do it is probably to use two CAT5 Y splitters as follows:-
|<------------ Blue & Brown pairs only----------------------------------------------->|
PoE & Data----->| |<--------> to Camera
|<-------All 8 wires to RB eth0---> RB <-----Orange & Green Pairs from RB eth1---->|
Regards
Chris Macneill