"Special ready to use rescue stairs"? They may be painted Red and have Airport Emergency Services on the side but I'd hardly think they would be fast getting in place at the door. In fact it would be a brave Driver to approach an Armed door in those circumstances where he could end up with a slide in his face any second.
Pax going down a dual channel slide raft would exit the Jet much quicker as well if it developed and the stairs would only hinder a full EVAC.
So I'd be telling them to keep clear until the time when the Fire is under control and we are then not using the slides. i.e. After the Fire is out and not before...