Depends on what things you need to do. Since we don't support many of the events of those platforms, yet, it might require some additional platform specific code for handling multitouch etc. But for the graphics, yes, that's working with the same code base.
I have successfully coded a game for windows, mac, iphone/ipad and android using the same c++ code base and irrlicht as a base engine (but with a lot of modifications). So it is possible, but requires some time.
