It's 4 conductor 22 Gauge solid. Standard ADT alarm wire. Hey, there's a clue!Is that 1/4" copper for pneumatic controls or is it a single conductor strung thru out the building?
The old hospital I worked at had a 1960's paging system. It's antenna was a single conductor looped on each floor with a center core riser.
Both of these systems has the beams drilled like that for both protection and to insure placement.
Granted it was a federal hospital were $$$ wasn't an issue.