The three firms that own most cable systems in the Northeast US have struck a roaming deal for current and future Wi-Fi networks: I've written extensively about Cablevision, the New York, New Jersey, and Connecticut cable provider that's put hundreds of millions of dollars into outdoor Wi-Fi deployment for its customers. Comcast and Time Warner Cable were widely rumored to have similar, perhaps less ambitious plans on the books, and Time Warner Cable has deployed some Wi-Fi hotspots in Manhattan, Queens, and at LIRR rail stations.
The roaming relationship for the three firms allows customers to use their own cable company login to access Wi-Fi across any hotspots operated by the three companies. Because the firms have virtually no territory overlap in service, they can pursue this cooperation as a full-court press against Verizon. Verizon has a paltry and restrictive free Wi-Fi offer that works only for a subset of Windows laptop users.
Providing outdoor data so extensively and free to cable broadband subscribers lets these firms sell "home" broadband as an extended alternative to 3G data pricing plans, whether for the iPad or MiFi or what have you. If you can service in most places you travel over Wi-Fi as an exclusive subscriber benefit, that might offset the $60-per-month plus overage fees cost of a 3G broadband plan (plus the two-year contract commitment).
This announcement doesn't seem like a prelude for Time Warner Cable and Comcast to start building out Wi-Fi in the rest of their respective territories; both have a relatively small footprint in the Northeast compared to the rest of their network operations.