Perhaps no expectation of privacy from the folks on the street, but the footage is privately owned. By insisting that the businesses purchase, install, maintain, and store the camera's and footage, the businesses own the footage, and it is subject to fourth amendment protections. "secure in their .... papers".
If the city wanted to require hosting a city owned and maintained CCTV system as a pre-requisite for business licensing, it would be odious, but probably legal, but they cant force the businesses to open their privately owned files without a warrant.
For that matter, "expectation of privacy" could get dicey depending on what, exactly, Houston considers "video coverage from the exterior of the building to the property line" Does that include areas out of public traffic and sight? Like fenced off employee or owner only areas? back yards? Fenced private property adjacent to the businesses?