At my old house I picked up pager traffic on a software defined radio and decoded it. Everything I’ve ever seen has been unencrypted.
Basically the pulses come from the towers the first X number of pulses are the address kind of like the phone number for the pager. All pagers listen to all pulses and just ignore the ones that aren’t addressed to them.
Here’s some details on one of the more popular protocols
It would be nice but you’d have to go back to 1850 because we eradicated them and made sure it couldn’t happen again.