I think we have argued this in the past and I disagree and, of course, that was also not the question. Since the question was only related to whether he could use the existing wiring, the answer is yes he can use the same coax but needs to run a new control cable.
As to running 3 coax cables, 3 to where when there is likely already one running to the front and one running to the rear. Even if you install a Hopper/Joey setup you can install the Solo Node on the roof and use the existing coax for both. Only if you wanted to install 2 hoppers (or a Hopper and a Super Joey) would you need the 3rd cable and that connection can be made on the roof as well.
