My assumption (because we have no evidence to support or contradict it) is that in normal zones, there are medi-beacons that provide transport for ALL defeated entities (heroes/villains, etc), like the one in Skyway [https://hcwiki.cityofheroes.dev/wiki/Healing_Node_Badge]. As for hazard or trial zones, I think they have their own hospital sites for players, but nothing would stop the use of those same medical facilities on defeated enemies (Hippocratic oath and all).