We think the batteries will work in both phones. There are different apple part numbers (APN) for the batteries but that is common for iPhones even within the same device. We've tested all possible combinations of APNs and iPhones and have not had an issue. We have just listed the part we sell as compatible both for the AT&T(GSM) and Verizon(CDMA) iPhones. Check it out here.
We took a sample of 5 iPhones we have around the office that were purchased at different times. 4 were AT&T and 1 was Verizon. 3 of the AT&T batteries had an APN of 616-0513. 1 AT&T and the Verizon iPhone had a battery with an APN of 616-0520. That means that Apple was using the APN 616-0520 for both models. It was also the official white iPhone that had the 616-0520 battery which came out around the same time as the Verizon iPhone. The batteries we sell carry a part number of 616-0521 which works fine in both iPhones in our own internal testing.
We will keep an eye on customer feedback just to make sure that we don't run into issues but at this point we think the batteries are cross-compatible.