AT&T just reported a solid third quarter that saw its total subscriber count pass 100 million for the first time. Of course that milestone will be crushed if the carrier’s $39 billion T-Mobile USA acquisition is approved, but for the time being it represents a solid strategy that is clearly working. A huge part of that strategy moving from 2011 into 2012 is rolling out 4G LTE service across 15 cities, the first five of which went live last month:¬†Atlanta, Chicago, Dallas, Houston and San Antonio. AT&T has yet to reveal the remainder of the 15 markets it intends to blanket with its next-generation 4G service this year, but BGR has uncovered two previously unannounced cities named within the carrier’s presentation for its upcoming earnings call. According to AT&T’s slide deck, both Boston and Washington DC will see the carrier’s 4G LTE service go live this year and judging by some of the speeds we’ve seen so far, residents should certainly be looking forward to it.