Q-Signals got back to the days of Morse Code only radio transmissions...they are brevity codes that made it to voice. Florida is the only place, aside from Amateur Radio, where they are used tha I am aware of.
On a broader note, the use of any brevity codes can cause confusion outside of their home jusridiction. The latest "craze" is to use Mobile Data Computer/Terminal codes on voice. Our local Fire Depatrments use AOR Availible On Radio, AIQ Availible in Quarters, AOS Availible On Scene and so forth. This is not clear text and can lead to confusion on Mutual Aid Incidents. At some point true clear text, say what you mean, will become the norm, but I am guessing that is a generation away. It seems to take that long for a change to take hold.