Verified answer

Many agencies do. The federal government tried without much success to get everybody to use plain language. A few agencies did already. Many agencies made some effort to switch. But now things are almost back to pre-2001, at least as far as that goes.

All the time and even more as Police have had to make new codes to cover new age crimes and terrorist crimes and such but yes codes are still very much still in use today, and are also using more and higher secretive frequencies too

Yes.