I'm confused. How could there possibly be no wires or pipes in between the shared walls?
I guess I could see how you could get away with it in terms of pipes, but wires? If you couldn't put wires in shared walls, then like 80% of the wall space on your average townhome couldn't have an outlet. I have plenty of outlets on my shared walls. Pretty sure one of my shared walls has plumbing too because that's where I had a water leak. Quite frankly there is hardly any additional wall space left for an outlet if the shared walls couldn't be used for outlets and switches.