Now why didn't I think of that? I've been pondering how to remote my IQ4 from the battery charger and this is a great way to do it.
I'd open up all of the phone outlets first to ensure that the highly-trained installation worker got the color codes right, and that all four wires are run, not just two. Other than that, I can't think of a reason why this shouldn't work. It is possible that the phone wiring may pick up some differential-mode interference that affects the charging, but you should be able to tell if that happens.
Mad Scientist and Principal Operator of 2008 Newmar Ventana 3933