Comment by adrian_b
The reason for using pagers instead of phones is that they are receivers only, they do not transmit, therefore they cannot be localized.
So no data exfiltration was possible using the pagers. The only purpose of the modified pagers was to maim or kill their possessors, by detonating all of them simultaneously.
Some kinds of receivers can be localized because they convert input frequencies to a standard internal frequency for more convenient processing. See https://en.wikipedia.org/wiki/Superheterodyne_receiver#Local...
It's how the TV detectors work in countries, such as the UK, that charge a license fee for TVs.
Military radios can't use this common technique because of the risk of detection.
I suspect pagers only receive on 1 or at most a few frequencies. If that's correct, they wouldn't need that technique.