AT&T is throwing a free HBO subscription into its 'unlimited' data plan

AT&T on Wednesday announced that subscribers of its "Unlimited Plus" mobile data plan will soon receive a subscription to HBO at no extra charge.

The promotion will go into effect on April 6, and will apply to both new and existing subscribers.

AT&T says that "Unlimited Plus" subscribers who pay for HBO already through one of the company's video services, like DirecTV or the DirecTV Now live streaming service, will now get HBO for free. Those who don't use one of AT&T's video services can redeem the channels through DirecTV Now or the HBO Go app. And those who subscribed to an AT&T video service, but not HBO, will now get access to the channel automatically.

Previously, you could add HBO to the DirecTV Now service for an additional $5 a month, though AT&T recently gave those who subscribed to DirecTV Now's higher-end bundles a free year of the channel. DirecTV Now starts at $35 a month on its own, though the "Unlimited Plus" plan includes a $25 monthly credit that can be used toward the service (or standard DirecTV, or AT&T's U-Verse TV service).

The move comes at a time where AT&T is on the verge of purchasing HBO's parent company, Time Warner, for roughly $85 billion. It's also likely to raise concerns related to net neutrality, or the principle that internet providers like AT&T should not give preferential treatment to certain services, particularly ones it owns.

AT&T already exempts its video services from counting against data caps with its non-unlimited plans, and CEO Randall Stephenson has hinted the company will do the same once with Time Warner properties if it completes the deal. That specific practice doesn't apply to AT&T's unlimited plan directly, but the idea is to make it so AT&T can control more of the stack that covers how you connect to the internet, and what you watch over it.

Along those lines, David Christopher, the marketing boss of AT&T's entertainment group, said this is just the beginning of the carrier incorporating entertainment services in its bundles.

"We are just getting started," Christopher said in a recent interview with Business Insider. It's part of a "better together philosophy" with wireless service and entertainment, he said.

Nevertheless, the promotion looks to be good value today, and marks the latest attack in the ongoing "unlimited" plan war between the big four mobile carriers in the US. While none of these plans are truly unlimited - you'll still be at risk of slower speeds if you use a certain amount of data per month, and you only get a certain allotment of mobile hotspot data at LTE speeds - they do represent a shift away from the tighter data restrictions of recent years.

AT&T rebooted its offering in February, renaming it "Unlimited Plus," and making it available to all subscribers (previously it was only available for those who subscribed to one of its TV services), and dropping the entry price from $100 a month to $90 a month. It's still the most expensive of the bunch to start, but throwing in HBO may give it a boost as it attempts to catch up to Verizon in total mobile subscribers and fend off the continued growth of third-place T-Mobile.

Additional reporting by Nathan McAlone.