re: How many people and time do you think it would take just to visit each one of those apartments, assess the situation, come up with a plan and arrange proper logistics support?
That would not be necessary nor at all practical under the time constraints. Take a random sample to access the situation and needs and plan accordingly.
Why would it not be necessary? How would you take care of 49K people in 19 multi-story apts in a city of 8M? How many vehicles do you think it would take to move just those 49K? How would you even tell people help was coming and for them to get ready?