That would be an odd choice, but maybe the size requires it? I'm no expert, but I would think the size of the garage wouldn't make a difference between prefab supports and poured on site. Obviously the ground floor itself would be poured on site, but otherwise, I would expect prefab for the rest. The smaller pieces like stairwells will be telling, I think. If they pour those on site instead of trucking them in...
Meanwhile Universal's TM parking garage going the prefab route has a complete stairwell and a ton of the outer support beams and walls in place within the last two weeks.
EDIT: More like two stair wells, portions of upper floors, and more support beams around the second stairwell as of about noon today!