A land line makes an actual circuit to the other party. The signaling information is used to arrange the necessary relays/switches (for old analog gear) or virt

A land line makes an actual circuit to the other party. The signaling information is used to arrange the necessary relays/switches (for old analog gear) or virtual circuit routing tables (for newer stuff). Once this circuit is setup, there's no requirement to actually monitor the electrical signaling on the wire (physically or virtually) until the next out-of-band signal event (e.g. hang-up), just as there's no requirement for UPS to open your box while it's in their possession. Even for virtual circuits you don't need to inspect the data portion of the segment, you need only inspect enough of the header to send it on to the right endpoint. But either way, even that argument has a bit more nuance; the call metadata was a business record retained by the business itself, not the person. And the person knew the business had these records about them, because the phone company mailed them that metadata every month along with the bill. So (the argument went) there couldn't be a reasonable expectation of privacy regarding the phone numbers dialed and the call lengths, since the phone company made it quite clear every month that this "metadata" wasn't actually private (to the person) at all.