I have never seen these on the roof, however, I have seen them posted on telephone poles and light posts all throughout Chinatown
There isn't any single company that supplies those, but there are a handful of security dealers that essentially assemble them.
That one looks like it might be old, the PTZ on the bottom looks like a really old Pelco unit.
Many cities are starting to deploy these municipal surveillance boxes, many with grant funding. So, it's hard to say which are real and which are not anymore.