It’s not exactly Aereo, but startup NimbleTV — which offers existing pay-TV subscribers access to their channels and DVR recordings over the Internet — has attracted the attention of industry lawyers who are examining whether the service is legally in bounds.

NimbleTV initially launched in New York late last year for subscribers of Cablevision Systems‘ Optimum, Time Warner Cable, Verizon FiOS and RCN. On Wednesday, the company announced its expansion into in the Chicago metro area to residents with existing Comcast Xfinity and AT&T U-verse TV subscriptions — and said it plans to roll out to several other major U.S. cities later this year.

The startup doesn’t have deals with any of the cable or telco TV providers. Instead, it confirms users’ existing subscriptions and channel lineups through operators’ online portals and then streams live TV and DVR recordings from its centralized data centers to various Internet devices.

Anand Subramanian, founder and CEO of NimbleTV, insists the service is fully legal and simply lets users with verified pay-TV subscriptions access programming they’re entitled to over the Internet. Because NimbleTV requires a paid subscription, the service doesn’t circumvent the economics of the industry, he said.

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“We have been actively doing this for nine months now,” Subramanian said. “We’ve talked to everybody in the industry. Everybody knows what we do.”

But currently, at least one operator has initiated a legal review of NimbleTV to determine if its service is kosher. “They’re looking into NimbleTV right now,” said a source at the pay-TV provider, who requested anonymity because the investigation is internal.

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To Subramanian, NimbleTV is just a virtualized version of Slingbox and — unlike Aereo — all the programmers and operators are still getting paid by their customers. “We are brutally insistent on requiring a subscription,” he said. To subscribe to a particular NimbleTV package, customers must provide a home address within the region where the service originates.

Aereo, whose backers included IAC’s Barry Diller, was effectively shut down by a U.S. Supreme Court ruling in June finding that the startup’s service infringed the copyrights of broadcasters by streaming over-the-air TV signals online without permission. NimbleTV is essentially applying the Aereo model to pay-TV, hoping to stay out of legal hot water because it isn’t trying to provide an alternative to subscription television.

Subramanian declined to reveal how many users NimbleTV has signed up so far. He had previously claimed nearly 80,000 people had registered to test the startup’s beta test in NYC last summer.

NimbleTV provides streaming video to multiple devices, including Roku and Apple TV set-tops, web browsers, Apple iOS devices and some Android devices. The company is offering basic live-streaming of live TV for free, as an incentive for users to sign up. NimbleTV makes money via its cloud-based DVR service, starting at $4.99 per month for up to 10 hours of recordings.

Founded in January 2011, New York-based NimbleTV has raised about $6.5 million in funding from Tribune Media, Greycroft Partners, Tribeca Venture Partners and angel investors. The 25-employee company is based in midtown Manhattan.