Adam is correct. The two packages have no interface as such, but PI output is completely compatible with Vegas (or any other NLE). The bit about alpha channels only applies if you want to add the PI output on top of another video stream e.g. add an explosion to a video clip. The only ‘gotcha’ I’ve found is that only some codecs allow alpha channel info – if you pick a codec that doesn’t, PI will grey out the alpha channel tick box.