Comcast's live streaming TV service has launched in the Boston and Chicago areas, with plans to bring it to Comcast's entire cable territory by early next year.

We asked Comcast today if Stream TV usage will count against the 300GB data plans imposed in certain parts of Comcast's territory. "No, Stream is an IP cable service delivered over our managed network to the home," a Comcast spokesperson replied.

Comcast also pointed Ars to an FAQ that says, "Stream TV is a cable streaming service delivered over Comcast's cable system, not over the Internet. Therefore, Stream TV data usage will not be counted towards your Xfinity Internet monthly data usage."

Stream TV also doesn't use a customer's allotted Internet bandwidth, as measured in bits per second, Comcast told Ars. For example, a Comcast customer who pays for 50Mbps Internet speed would still have a full 50Mbps for other online services while using Stream TV.

Stream TV is intended for Comcast's Internet-only customers, offering live TV on computers, tablets, and phones. In-home streaming video is delivered as a managed service over the Comcast IP gateway in customers' homes and works similarly to cable TV—despite not requiring a cable TV subscription or set-top box—potentially providing greater video quality than rival streaming services. Sling TV customers, for example, have experienced several outages.

Comcast has steadily introduced monthly data caps into new areas, testing customers' responses before a potential nationwide rollout.

There is no specific rule preventing an Internet service provider from exempting its own streaming video from data caps, even though such a practice could disadvantage competing services that deliver video to customers over the Internet. However, the Federal Communications Commission's net neutrality rules allow for complaints against so-called zero-rating schemes, with the commission judging on a case-by-case basis whether a practice "unreasonably interferes" with the ability of consumers to reach content or the ability of content providers to reach consumers.

The net neutrality rules also have an exemption for "non-broadband" services, or "IP-services that do not travel over broadband Internet access service."

An FCC spokesperson declined comment on Comcast's streaming video service not counting against Comcast data caps.

When Comcast bought NBCUniversal, it signed an agreement with the government that says if Comcast offers capped or metered Internet service, it can't treat its own network traffic differently from rivals' traffic. But that apparently doesn't apply to Stream TV since the in-home streaming isn't traveling over the public Internet.

Netflix, the biggest online video provider in the country, has previously criticized Comcast's caps but declined comment when contacted by Ars today.

"Stream TV" costs $15 a month and lets customers watch live TV channels while on Comcast home Internet connections. It doesn't provide the same flexibility as streaming services like Netflix or Sling TV, which work the same on any Internet connection. Outside of the home, Stream TV offers access to on-demand and recorded videos, and customers can use their Comcast username and password to sign into channel-specific applications like HBO Go.

The Chicago metro area launch is happening today, Comcast said in an announcement. Comcast's July announcement said Stream TV would launch across the company's entire territory by early 2016, and Comcast says it still expects to hit that timeline. The rollout has gone slower than expected, though. Comcast initially said it would be available in Boston by the end of the summer. The Greater Boston deployment finally occurred last week and includes eastern Massachusetts, New Hampshire, and Maine, according to the Boston Business Journal. The data limits and overage charges haven't come to Boston and Chicago yet, but they do exist in Maine and about a dozen other states.

Stream TV's live programming includes HBO, ABC, CBS, CW, FOX, NBC, PBS, Telemundo, Univision, and local channels that vary by market.

The service launch comes as Comcast continues to add Internet subscribers while dropping TV subscriptions. In Q3 2015, Comcast gained 320,000 broadband subscriptions for a total of 22.87 million, while losing 48,000 cable TV subscribers, dropping to 22.26 million. The thirteen largest pay-TV providers overall lost 190,000 video subscribers in the quarter, up from a loss of 155,000 in the same period a year ago, according to Leichtman Research Group.

This article was updated with further explanation from Comcast, more details on the FCC's net neutrality rules, and requirements from Comcast's NBCUniversal merger conditions.