Of course E* carries Sportsouth HD but not NESN. go figure.
Dish shows every game in HD that's available to them in HD. The factors are:
1.) They don't have an HD contract with some RSN's such as NESN, MSG, and FSNY.
2.) Some nets produce 100% of the games in HD, some 50%, some 10%, etc. Check out nhl.com to see a schedule of HD games on all nets. For example, I believe NESN is producing all bruins games in HD.