This isn't entirely true. Cellphones are actively transmitting and checking in with the towers, so they're pretty easy to track. Walkies transmit sporadically,

This isn't entirely true. Cellphones are actively transmitting and checking in with the towers, so they're pretty easy to track. Walkies transmit sporadically, so they can be tracked when activated. It's not instantaneous, but with a decent logging system you can keep track of users to a large degree. Even when you have multiple units all of the same model on the same frequency, there are various tricks to sorting them out to individual units. One-way pagers don't transmit typical signals, buy like all RF devices, they're still emitting some signals and are trackable to a large degree with an antenna network deployed for that purpose. You might not be able to track them deep within enemy territory, but there is still a lot that can be done to track general movements or to find where clusters of the oscillators associated with the pagers turn up in large numbers.