I don't think there is an opening from the roof rack into the vehicle interior. From the instructions at H and A, it appears that there are 4 plastic covers which conceal the external mounts. The roof rack just bolts onto these mounts.
It would see that you would have to do a bit of drilling to get the light bar installed. Down the road, someone may come up with one that does not need it, but as of now, it seems like you gotta make a hole.