Please don’t refer to laicized priests, or even priests who have left the active life but are not laicized, as “ex-priests.” There is no such thing, as the mark of priesthood is for ever. Even priests who have left the Church are still priests, just as you and I, even if we became athiests, would still bear the mark of baptism.
In the event of an emergency, laicized priests (and, I would assume, non-active priests) have the duty to hear confessions and give the last rites. My husband, who is a laicized priest, has done both in the absence of an active priest. In fact, the priest at our parish wants my husband to have the oil for the annointing of the sick on him in case he is called to an emergency. We live in an area with few priests. If our priest were at a distant parish, it could take him hours to get back to our area.
I think an order from the Pope could be classed as an emergency.