The RSN's in HD on Dish are a crap shoot. They do not carry them 24/7. They have only so much bandwidth so they pick and choose which games to show in HD.
The channels are in SD 24/7 but as for how many games you'll see in HD I dont have a definite answer
It does look like that from our end as sports fans - but I had a chance recently to chat with someone who is dealing with the issues internally.
It turns out that most of the games we do not see in HD, are not available to Dish for technical reasons.
For example, in several cases, the RSN is owned by a cable system, and "mysteriously"

they have a fiber feed to their cable head end, but no such feed to Dish, and some games do not end up being uplinked by the provider, so Dish ends up only with the SD feed.
They are trying to get these situations resolved, but the providers do not have incentive to make it equally available to Dish as to their cable head-end.
Yes, for the Dish customer, the end result is the same, that we do not see all the games in HD.
But it is not being done to save bandwidth.
PS It also seems likely that we will not see 24/7 HD RSNs until there are no more popular national HD channels missing from Dish's lineup. I think that will take both E*14 to Western Arc, and the new Eastern Arc satellite (E*15 ?) to both come online, as a minimum.