Im guessing they mechanical turk (https://www.mturk.com/mturk/welcome) the crud out of these images, taking 3 or 4 photos at the same time of day and if there is a person in the first image then replacing it with the second, i came to this conclusion based on the fact the whole damn city looks like its apocalyptically empty once you get off the ground. None of the office buildings have meetings on and very few windows have people in.