You aren't supposed to use elevators during a fire and they usually return to the ground floor and stay there if there is a fire. That's true of all buildings, if the Park Plaza has a fire the evacuation will be by stairs also.
The fire department can operate the lifts to evacuate disabled people if they think it safe, or they can be carried down stairs if the lifts are inoperable. The stairwells of the Hyatt are behind fire doors from most of the building, so should remain usable even if there is a fire in the middle of a floor.