The next step in shutting down former Alltel in Georgia is underway: http://www.phonescoop.com/articles/article.php?a=15007
Of note, AT&T's commitment to keep CDMA live in these markets expires June 15, 2015; I'd be surprised if they keep it on a day longer, which means a fallback to 1x on Verizon for Sprint customers roaming off the interstates and a few other corridors in south Georgia. The SouthernLINC RRPP buildout can't come soon enough...
I believe this is by Cellcom, a Wisconsin based carrier.
Marquette Michigan is not yet included. These areas include locations where Sprint through Clearwire had WiMax sites, the only 4G in the UP for many years.
Extended LTE may not have all the Sprint features, but counts as regular data usage towards your plan. This should mean regular LTE speeds.