You can achieve a non-hand brake slide in a Cooper S, I've witnessed it as well as been in a Cooper S while it was doing it. You just lift off the throttle before going into a corner and you get oversteer, or you can do a Scandinavian flick. If you don't believe that then just go onto YouTube and look up FWD drifting, it's quite possible.
** Granted it's not done in the same way a rear drive vehicle, but like everything in the automotive "stunt" driving world there are a ton of different techniques. But if you want to go by the textbook definition of a powerslide then no, that isn't one, but neither are a lot of the other cars in this thread.