No answer to your question, just more questions to narrow down an answer... As far as what camera can export still shots, I don't know - hopefully others will. But still shots of unusable images don't do you much good regardless. :)
What is the FOV the camera is supposed to cover?
What evidence do you want the camera to provide? i.e. do you want to be able to identify faces? (PPF?)
A camera on top of a 4 story commercial building is ~50 high - what is the angle of the camera in relation to the scene it is covering? i.e are you shooting straight down on the sidewalk below (~50 ft distance; ~90 degree angle), or are you shooting across the street at that sidewalk (~75 ft distance; ~45 degree angle)?