Yes, I would agree on the Average Joe listener not having the capabilities to monitor Pro-Voice. But, I have noticed that many LE agencies of questionable character such as San Antonio often use encryption or Pro-Voice. This is based on my opinion and the opinion of others (Texas Monthly).
When I worked for TDCJ-ID, the agency used to dump parolees in San Antonio, Lubbock, El Paso, Houston and Dallas for the most part. Later, they began returning offenders to the county where they fell.
On the other hand, I can see why Bexar county uses Pro-Voice. The Texas Syndicate, Mexican Mafia and other prison gangs flourish there. For the most part, LE officers are grossly outnumbered.