Midtown Atlanta? Now you're talking my language. I live between Midtown and Buckhead off Peachtree. But I noticed the same thing. All of the 800 acceptances thus far (at least that we know of from Robert's source) have been outside the Perimeter (I-285 for those not familiar)...off to the south and east. However, the reach of 800 is greatly improved over the propagation characteristics of a 1900 mhz signal so it's possible you connected to one of those. But I think the more likely scenario here is that new towers have had 800 voice activated closer to or within the city and that is what you are connecting to based on your signal strength deep inside the building you work in. I just don't think you'd have had such a strong signal from a tower so distant and outside the urban core. I would also venture to guess that even though 800 covers a pretty large area that the RF engineers have adjusted the downtilt more (in those southern and eastern suburbs) than those towers would be if they were in a truly rural area.
All of what I'm saying is pure conjecture at this point and I guess we'll have to wait and see what the next round of 800 voice acceptances shows when Robert posts it.
That said...I just updgraded to signal check pro to see if I could get 800 voice and...so far, not yet.