Is it for some actual life safety purpose (i.e. console decode) or just to make a radio sound cool and therefore irritate everyone else on the channel? The MFCG has documentation and/or policy covering most things on the conventional interops, but I can't recall off the top of my head if data/signalling is prohibited.
It is for our Accountability. Engine Operator and Accountability Officer keep track of the IDs on our Tac Channels, but on mutual aid calls we don't have any IDs. We figured we would add it to every channel as Radio IDs are probably going to become a County-Wide thing.