It turns out Apple is NOT able to use the pre-qualified number I got from AT&T. Luckily, I asked the Apple rep only a few minutes after I got in line. Unluckily, I then went to an AT&T store, which sold out with about 10 people ahead of me in line.
Normally I guess it wouldn't be a big deal to have my credit run twice, but I'm planning to move shortly and need to keep my score as high as possible. Also, I had anticipated paying a deposit and think part of the reason that I didn't owe one was because I told the rep running the check that I have AT&T home phone service. He asked me for that phone number as part of the check, and I suspect having paid that bill on time for 10 years probably worked in my favor. Not sure it would be the same result at Apple, and I didn't want to wait in line for hours to find out.