Sure. Absolutely. But if they'd been straight PSTN lines the abject process failure you've correctly described wouldn't have been able to put lives at risk beca

Sure. Absolutely. But if they'd been straight PSTN lines the abject process failure you've correctly described wouldn't have been able to put lives at risk because we'd have had to call the telco who most assuredly would have known what the lines were for, and we wouldn't have been able to shut them off. Safety critical systems need to not rely on humans doing boring, complicated things correctly for long periods of time.