Unfortunately these are not easy questions to answer. The NXTCam actually contains two processors each of which is re-programmable. One looks after the camera the other performs system start up and handles communications with either PC or the NXT. If the communications device needs to be reprogrammed then the leJOS API will not work (a new driver will be required). If only the main camera processor is re-programmed then the leJOS API may continue to work. Without spending time (which I'm afraid I don't have), looking at the code then I can't really say for sure. I would suggest that you contact the author of the modified firmware that provides the functions that you want. His blog can be found here...
and I think you can contact him from this page...
Good luck and be sure to let us know how you get on!