My guess is they are isolating the background or field mics and running a parrallel out of phase? Haven't heard the comparison though. If it's in stereo that would leave a 'hole' in the middle for a mono vocal (mixed in later) to sit in nicely.
It's pretty shabby for the solution to have taken them this long BTW.
I haven't been able to watch a heap of the games, not cause the horns but rather the lack of excitement.
Until it gets to the pointy end most games are so defensive and boring to protect the aggregate scores.
Minimise a tad maybe but then you dull down the clarity of commentators too. 
