Exactly. AT&T got smart here. They are on a wait and see approach to prevent any shortcomings Verizon might and will encounter (random things happen when implementing a new network).
Yes. In addition, much of the LTE spec was left open, so someone has to fill in the gaps.
Basically, AT&T is staying at least two years behind in LTE, which they feel is a good plan, and probably is.
In any case AT&T is also layering their entire backhaul in fiber so that when LTE goes live, AT&T users see those 50Mb/s speeds in real life. Where as Verizon is going tower by tower by tower approach.
Both carriers have to do a tower by tower upgrade, preferably using fiber or microwave.
Verizon Wireless hired Verizon's landline side to upgrade all their towers with fiber by 2013, when LTE is fully rolled out. AT&T
recently stated that they will still be deploying fiber backhaul through at least 2015.
Also, Verizon bought MCI back in 2006 specifically because of their major national and international fiber trunks.