The Bell System was, in modern parlance, fully vertically integrated. They didn't own the mines that the copper for the conductors was extracted from. And they didn't cast the copper ingots. Though they were interested in the metallurgy. Because they drew their own wire. And cables. And transformers. And vacuum tubes. And so on. It was all in-house. They even treated their own telephone poles. So something like a practical survey of various types of preservative treatments for wood was in the remit of Bell Labs just like the physics of a vacuum tube. Almost everything in science was in the remit when they had such a broad mandate. The Bell System had elements that almost resembled a kind of state within a state. (Part of why it was killed off -- antitrust violations.)