I did not think about wiring inside the pipe but that could still be accomplished by drilling a hole into the pipe to insert the wires on the other side of the point where the pipe is flattened and bolted to the base.
Terry
Terry, I thought about that, flattening, then drilling a hole and then protecting the hole so it doesn't fray the power wires, But the seller used "flexible" pipe so the handset could be moved to any position the owner wanted it to be when lit. That type of tubing is hard to flatten and when flat, would be more difficult to mount because it is not a solid pipe. So, I think the best mount would be a strap of some sorts. Or welding.
So, should you or I buy it to find out how it was done?

Whatever she did, the phone is trash and will never again become a working telephone. Not worth the cost of restoration for that common phone.