I am assuming that considering their limitation on bandwidth, sporting events on game only HD channels is pulled from a pool of shared bandwidth. When other scheduled HD sporting events come on at their previously scheduled (overlapping) time, they need that bandwidth and get it. The bandwidth was scheduled to go to them at say, 4PM EST. It wasn't the fault of the fans of the other team who were waiting for their HD game that your team had a rain delay. If they (Dish) don't have the bandwidth, what are they going to do?
Thank God I am not a baseball fan. I suppose when the day comes that hockey has more of their games in HD, I will find this to be a problem too (only with DirecTV, not Dish). But I only get 20 or so HD games of my team a year. Those are the special treat games that I mark on my Outlook Calendar to be sure to watch, so I am pissed when one is messed up. Cable, on several occasions, would forgot to turn the switch on for the HD feed on the game only channel. I used to get so mad.
Think though about that pool of HD bandwidth set aside for sports. There is a lot of stuff going on right now. Baseball, Nascar and other racing, olympic qualifying events, Wimbeldon Tennis, golf, the Coney island hot dog eating contest. That is a lot of bandwidth to bring the fans the HD feeds.