The house was built in 1951. The bathroom has been the same for thiry years. The tiles did not use backing board or wonder board. Just attached to the concrete attached with wire mesh. There is a pair of white wires running along the old tub. I do not know what it is. Whether it has power or not. Never heard of such a thing
Some of the wood has to be replaced . See pictures.
Your thoughts

If this were my call I'd be tracking those wires both ways. Let me know what you find.

I wonder if you can test the two yellow wires for current, without cutting them .
I have testers?

Old doorbell? Any sign of two white/yellow wires in the basement?