is there even a chance of making it into the cage successfully?
If the building is going to fail, no one is going to have time to get from whatever floor they're on down to the basement. And even
if they had the time to get that close to the shelter, I'd rather just make a left turn and head out the front door into the street instead of facing the risk of being entombed.
A basement shelter sounds good on paper, but in the real world, no one really can or would want to use it, particularly in places like China, Iran, Turkey or those kinds of seismically active countries that won't have robust emergency services to dig you out afterwards.
Actually, since many of the newer collapsed buildings fail because corrupt and greedy builders weren't constructing the buildings to the normal building codes in the first place, I wouldn't count on them constructing the "bomb shelters" any more robustly.