I can only speak for the one agency that I have intimate knowledge of:
Shotguns are carried with four rounds in the magazine, safety on, chamber empty, locked in rack in vehicle that has electric release and covers the trigger entirely with steel plate. Officer carries fifth round on person, and slugs are carried in duty bag (so, if slugs required for animal control, shotgun must be unloaded, then reloaded at roadside).
This agency does NOT use less lethal 12 gauge ammo.
SOme agencies do authorize it, even though statistically it's way more dangerous than say, the taser, and less effective. It is, however, a tool that may be useful. Personally, I am big fan of the CS gas rubber buckshot idea for crowd control (having been downtown Vancouver in the midst of the hockey riot, I really, REALLY hate crowds!).
An orange stocked shotgun would immediately indicate which one was loaded for buckshot, and which one had less-lethal. Last time I checked, the first rule of firearms safety for self-defence a al LEO was MAKE SURE IT IS LOADED prior to starting your shift. An empty firearm isn't much use to Police or public safety.
And yes, negligence ALWAYS gets someone hurt. 300 car crashes per day in the Vancouver area, most probably caused by someone's negligence...
Just my thoughts - Less lethal makes things more complicated, but sometimes makes the Liberals feel better.
Neal