The largest house we have re-wired for C-Bus was over 1000 sqm, concrete suspended slab and two levels of 3m ceilings plus voids. The client lived in England and the house was in Brisbane. We re-wired the whole house for C-Bus without ever meeting each other in person. All discussions were done via email and a few phone calls. We also updated the AV in the home which included distributed music and upgraded home theatre room. One other thing we were proud of was that not one extra hole needed to be created for access. Thankfully many downlights and existing speakers already installed gave us extra access through the ceiling spaces.
Below is a picture of the front of the home in question.
Clipsal C-Bus even have a wireless battery operated switch so you can have a switch on the wall where there are no wires at all.