They can't. VZW bought it years ago and they're already updating their antennas nationwide to the newest RRUs to deploy on AWS. AT&T had an almost nationwide slice, but they had to give it to TMobile. They have since acquired a bunch of AWS from various acquisitions.
(and just to keep it civil, I use AT&T. Have been for almost 14 years.

I have a VZW Mifi from work. I'm just calling out Valerie's constant BS)
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How is AWS already saturated? It's not even up yet.
Even if you are talking about 700, there are plenty of stupid fast speeds being reported all over the web and by reputable 3rd party sources, like rootmetrics.
Complete BS. Proof?
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Let's look at some stats from Philadelphia from July 2013.
http://www.rootmetrics.com/compare-carriers/united-states/philadelphia/philadelphia-pa-july-2013/
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Sprint is, by far, the worst in Phily.
T-Mobile's upload speeds are the same as your downlink. Since you claim to bench faster speeds than VZW, I'll love to see some tests over 3G and LTE showing an average of 12.5 down. This is what VZW is averaging in your market.
Where are these "better speeds" you claim?