Verizon is absolutely not the only wireless carrier doing this type of thing.

While in the employment of a certain "pin drop quiet" company as a Wireless Network Operations Manager, I was required to supervise the installation of hi-cap shelves (back in the circuit-switched days) that routinely routed customer's calls through it. No noticeable delay. No way to know if your call is being routed through it. Totally transparent to the end user. Able to record dialed digits / text (we called it Short Messaging Service) in those days) and voice if needed.

These shelves were connected via T1 circuits (1.544 MB/s) to various agencies at the local federal building. My staff and I only received enough instructions for installation and operations / maintenance - to ensure we could not be called upon to testify in any subsequent legal case / challenge.

This was post 9-11 from 2001 through 2004.