Probably possible - I don't see why not. Both should be 12V. Current might be an issue? Not too sure there...the extent of my electrical knowledge pertains to not letting the magic smoke out...
If you want a quick fix you could just solder the heated bed wire directly to the terminal, or to where the terminal is soldered to the RAMPS. Definitely be careful if you're soldering on your RAMPS board - failure there = a expensive mistake.