I believe he was simply asking for opinions on replacing the existing 3/4" valve with a new 3/4" ball valve.
Believe he mentioned having the city shut the water at the street a couple of places. If they don't have a problem with him replacing the existing valve, doubt there would be a problem.
Whether the existing work was done legally, is not going to mean much to anyone.
Edit: BTW...What makes you think that's a ground wire, going from a meter to the water pipe?
That black cap is likely the new electronic reader with a remote device outside the house(on the other end of the wire) for the meter reader to read the meter.