Is the back cover interchangeable with either iPhone 4?

It should be. The teardown did not seem to reveal any differences. We did not try it out yet, though.

Hope this helps! Let us know how it goes.

Because the new iPhone has both internal and external antennae, I recommend staying away from custom cases made of metal (instead of glass or plastic) until we know how it effects wireless performance.

Also, an official answer to this question from iFixit would be awesome.

Is the cdma back the same as the 4S?

I've seen conflicting answers to the question of whether the iPhone 4 back cover will fit the new iPhone 4S. Well I had to try it out for myself in order to get the answer.

Conclusion:

The iPhone 4 VERIZON/CDMA back cover WILL FIT the iPhone 4S. The iPhone 4 ATT/GSM back cover WILL NOT.

I searched eBay and purchased an iPhone 4 CDMA back plate and tested it on my iPhone 4S. It fits extremely well, no movement or wiggle. Everything locks into place just as expected.

However, I have yet to see a aftermarket back plate that didn't have the flash leak issue. When taking photos with the replacement glass plate, I get the flash leak. Interestingly though, another OEM white iPhone 4S I have also washes out the photo when using the flash. Not sure what to expect anymore.

No, the 4 clips on either side of the back cover on the iPhone 4 are spaced differently then the 4S. For more information, you can find me on kijiji.ca, just search my company name ---> Crystal Clear iPhone Screen Repair. I also replace other components in the iPhone including color conversion in a wide range of colors, front and rear facing camera, speaker assembly, battery and more. As well i do repairs on some other devices as well such as the galaxy note. You can find my Cell number and email address on my kijiji ad.

Thanks, Steve