Airfox
As Lozza says - very much a company thing. For the outfit I work for upgrades are strictly controlled - there are 2 scenarios - comp or comercial upgrades or entitlements or upgrades due oversale.
The first are usually pre advised due commercal reasons or due to the relevant seniority of a firm/subload passenger and cabin entitlements - for example an airport slot coordinator or senior airport manager might have an ID100 J class (or Y) ticket although s/he considered commercially suitible for a higher class - this is very company subjective..........
When I do oversale upgrades I upgrade firm staff travel first in priority order, then commercial upgrades (space available), subload staff - company staff 1st priority followed by other airlines staff followed by AD travel followed by the rest. Then the frequent fliers in order of commercial seniority and finally revenue commercial pax.
Having said that I do have the authority to upgrade as I see necessary due to any customer or operational reasons. I think most staff are astute enough to travel smartly and to make alowance for the possible - turn up in tattered jeans and a holey T-shirt and you won't get Y let alone J or F!!!