The article titled "AT&T flings cellphone network wide open" over at USA Today reads like a press release directly from AT&T. It states that AT&T is opening up their network to any handset, including Google's, and is just a PR response to the recent Verizon news to allow more phones on their network. Plus, it's not even new. You could take any unlocked GSM phone and use it on AT&T since...forever.
We talked to AT&T Wireless CEO Ralph de la Vega shortly after the Android announcement was made and asked them whether they would join the Handset Alliance. Their answer that their networks were open, and people are free to use any handset on their network because you can just plop a SIM in and go. We decided to pass on relaying this info to you, since you didn't need to hear something you already knew. So no, AT&T didn't just fling their doors wide open; it's just as open with handsets as its always been, but everything else remains the same, for better and worse. [USA Today]