I find it hard to tell. Cops at matches tend to dress like other competitors, IDPA vest, USPSA logowear. So it can be hard to tell the Sergeant from the dentist without getting into conversation.
Both organizations provide for duty gear wear not meeting rulebook specifications, but I very seldom see it done.
Which is something to think about; I know one deputy who did come to matches in full harness and had to learn how to negotiate some of the positions with restriction of bulletproof vest and laden belt. Reloading from a horizontal pouch with sticky Velcro flap is a challenge, too.