Sadly not. Unreal3 uses an older version of the engine. So unless epic gives us an update which will bring the engine number up to date we can't rebake maps in the udk and export it to unreal.
I could be wrong, I'm going purely by what I've read and guess work. However I'm pretty sure this is the case.
I also think I read some where that people wanted to make a new unreal game using ut3's meshes etc + new content to make unreal3 how they thought it should of been. However Epic won't allow this

The community could, I guess, make a unreal3 clone/rip-off legally (like those shitty knock off toys you get). So long as things are named differently, look different, and everything is scripted from scratch. But that's a lot of work.
ie, have a shock rifle but call it a plasma-rifle, have it look different, have the beam/cores a different color and call a combo something else should avoid copyright problems, I think...