AT&T makes $100/month unlimited plan available to all

AT&T fully joined the unlimited-data battle, announcing that any customer will be able to sign on to its plan without a DirecTV subscription.

The carrier’s unlimited data plan starts at $100 a month for the first line and $40 a month for each additional line. A fourth line is free, so an account with four lines costs $180 a month after two initial months at $220 each. AT&T launched the plan last year exclusively for DirecTV subscribers, but starting Friday any user can sign up.

“We’re offering unlimited entertainment on the nation’s best data network where and when you want to enjoy more of what you love,” said David Christopher, chief marketing officer of the AT&T Entertainment Group, in the announcement.

The news is only the latest volley in what has quickly become a vicious battle over unlimited data plans between the four major U.S. carriers. T-Mobile and Sprint were first into the breach when they rolled out unlimited plans in August, and Verizon finally announced an unlimited plan earlier this week in a reversal of its longstanding policy of avoiding all-you-can-eat plans.

And the stakes have increased as both T-Mobile and Sprint have sweetened their unlimited offerings. T-Mobile recently began including taxes and fees in the price of its unlimited plan, and Sprint lowered the price of its plan earlier this week, offering four lines for $22.50 a month each. Both Sprint and T-Mobile have also added HD video and 10 GB of mobile hotspot to their plans, matching Verizon’s offering but beating its price.

AT&T’s plan includes unlimited calls from the U.S. to Canada and Mexico and use of talk, text and data in Canada and Mexico with no roaming charges. But like other so-called “unlimited” plans, AT&T’s has some restrictions: video is downgraded unless users turn off the “Stream Saver” feature, and the carrier “may slow speeds during periods of network congestion” once users consume more than 22 GB of data in a given month.

AT&T has bled share of the postpaid smartphone market as it opted to focus on high-end users, sacrificing customers who generate lesser ARPU. It remains to be seen whether AT&T can claw back customers from T-Mobile and Sprint without matching their pricing for unlimited data.