If the sporting events are chosen by DirecTV ahead of time, it only has to be 1 stream (with 4 audio streams). DirecTV will then just combine the 4 feeds into one channel, and beam it to the satellite as 1 stream. Since audio streams barely take any bandwidth, I can see DirecTV using 1 single HD channel space for such a purpose. As a matter of fact, with events like the Australian Open and the Masters, they did just that. 1 channel that combined the other channels.