Well BTN has become either a standard channel or at least standard part of sports packages with most of the major cable providers, so the more expansion it does into major television markets the more money it will be making, regardless of how many fans of the DMA actually exists.
Its like with Rutgers... while Rutgers is the #1 college football school in the NYC DMA (the #1 TV market in the country - its made up officially of NYC, LI, Southeastern NY State, Northern half of NJ which by itself would be top 10 without being part of NYC TV coverage, Northeastern Pennsylvania, eastern CT) and has the largest amount of fans in the DMA, is RU really THAT popular the way that Ohio State penetrates in Ohio? Not even close. However, Rutgers is far more valuable that OSU purely in terms of the Cable subscription coverage for BTN because MOST people in the NYC DMA subscribe to some sort of cable-satellite service, and MOST sports fans will get the sports packages, regardless of being B1G or Rutgers fans. That's basically what Georgia Tech would bring to the table - regardless of how many fans they have, or their success, they'd bring the #9 DMA in the country which = $$$ in everybody's pockets in the B1G.