AT&T 3G MicroCell service spotted in Chicago?

So we're in the middle of testing our Sony Ericsson X10 here -- stay tuned for that review, by the way -- and in the course of flipping through the settings, we noticed something strange: it's reporting two 3G MicroCells nearby. Now, to the best of our knowledge, you can't buy a MicroCell in these parts -- sales are still strictly limited to a small handful of test markets -- but it makes you wonder. For what it's worth, SE shipped the phone with a GoPhone SIM, but we're not sure whether that makes a difference. We're looking into the situation and we'll report more as soon as we have it.