More worrisome for residents, businesses and elected leaders, however, is the trouble Verizon has had in bringing FiOS' fiber-optic cable from streets into homes. The 2008 agreement stipulates that the franchisee shall install cable service within six months after a request is received, a period that can be extended by six months.

Verizon doesn't deny it has fallen short, but wants to rework the rules to allow a different approach. It will also soon introduce "microtrenching" as a more efficient means of bringing fiber to homes.

In the meantime, some frustrated Harlem residents say they've been waiting years for FiOS.

"It used to be I called all the time," said Karen Martinez, a health care staffing executive who has tried to get FiOS since she and her family moved into their East 130th Street brownstone in the summer of 2012. "Now I call every few months. I understand Verizon is trying to capture big buildings, but a customer is a customer."

She has been told that some of her neighbors have yet to respond to Verizon's requests for permission to run cable along the outside of their buildings. A provider generally gets authorizations from each owner in a row of brownstones before wiring one so that all properties can be set up for service.

"Some of those buildings are abandoned," Ms. Martinez noted.

Verizon, based in Manhattan, has declined to provide the city with maps charting the street-by-street progress of its fiber network, citing the intense competition for cable customers. The lack of information about exactly where the service is available has contributed to concerns that the company has focused its "last-mile" deployments (from the street to the home) on upscale neighborhoods and has neglected low-income ones—a charge Bill de Blasio has made both as mayor and previously as public advocate.

On a more basic level, many residents have no idea that they can order FiOS and expect to have it within the six-months-to-a-year period.

"Consumers don't know whether this deadline applies to their building, because they can't easily tell whether it has been 'passed' by fiber," said Charles Fraser, general counsel for DoITT. "And from anecdotes we're hearing, we're increasingly concerned that Verizon has not made that information comprehensively and accurately available to its own customer-service operations."

Verizon denies charges of discrimination, pointing to the investment it has made in infrastructure in Harlem and other low-income areas. But it acknowledges it has failed to bring FiOS to all who want the service, blaming an outdated deployment model that isn't working.

"Logically, we would like to build as quickly as possible and satisfy customer demand," said Chris Levendos, vice president of national operations at Verizon and an architect of the FiOS network. "The challenges we've had over the last couple of years are because the process is inefficient, and we're focused on fixing that."