We knew they were coming, but AT&T just formally announced that its "Mobile Share" data plans will be available as of August 23rd. Just as we heard earlier, customers start by picking a data bucket starting at $40 for 1GB all the way up to $200 for 20GB. After that, devices attached to the plan come with requisite feeds between $30 and $45 per smartphone, with the price decreasing as you purchase bigger data plans. A 1GB plan carries a $45 per smartphone charge, 4GB plans carry a $40 smartphone charge, 6GB plans carry a $35 charge, and users who pick 10GB (or more) of data per month can add smartphones for $30 each. Tablets can be attached to the shared data bucket for $10, since they consume no voice minutes or texting data. Laptops, netbooks, and laptop connect cards can be added for $20, and standard cell phones can be added for $30. As for voice minutes and text messages, all of these plans included unlimited quantities of both.

Unsurprisingly, this plan has a lot in common with Verizon's new Shared Data plans — the major difference is the sliding cost of adding smartphones, though exact data bucket prices vary as well. Depending on how much data you need, your cheapest option will vary. That said, AT&T is throwing Mobile Share users a nice perk — you get unlimited mobile hotspot functionality regardless of which plan you use, so shared data can truly be shared across any device that can hook up to a Wi-Fi connection. To get all the details, this PDF has the full breakdown of AT&T's new plans.