I've seen the HOT-tag only once: After BA rerouted me from FRA-LHR on BA to FRA-LCY on LH, my bag had a couple of tags and one of them was a LH-HOT-tag.
The other tags are: 'RUSH', 'TRANSFER AT LHR TO TERMINAL 1 SHORT', 'PRIORITY' (all from BA), 'PRIORITY' (from LH), two tags from the Bundespolizei (federal police) and of course the normal baggage tag.

I've never seen a single bag with so many tags (8 tags!!!) (at checkin-in it only got the PRIORITY and the normal baggage tag from BA)!



P.S.: The bag arrived one day later in LON, but that's normal, because it's BA.