I found a new use for Warn's a few days ago, for a product launch - and that was to actually alert other people that a cue was coming up, as opposed to the operator.
Really big product launch, we had 6 bays of the Melbourne exhibition center (just for reference for any aussies on the board), and we had a small area draped off, making it seem like the event was taking place in part of one bay, and inside that it was set as a conference. Basically, the aim was to make it seem like a small product launch, as opposed to the rather huge, underwraps launch that it was. The drapes were on chain hoists, and we had a whole pyro/drape rising/blinders/dancers/theatrical thing, where this new product was being revealed. I needed the five floating techs to undertake certain safety checks, before the cue went underway, so it was a perfect time for Warn.
ie: "Warn Mech, talent in" was a warning to the floaters to ensure that the landing sites for our talent drops were clear. They had 60 seconds to raise any issues over comms before the cue was executed. "Warn Pyro, Flames on" was a warning to the floaters to check that the gas jets were clear and past the safety points. "Warn Mech, drape out" was a warning to the floaters to check that outside the drape line, no one was standing on the drapes, etc.
So warnings: not just for the departments. Also a good way to cue safety checks by spotters etc.