It seems that the SD broadcasts from U.S. sources are often clearer than the Canadian SD broadcasts.
My theory is that Dish gets the HD feeds on U.S. broadcasts and converts to SD broadcasts on those RSN's that they haven't contracted for HD. This gives a better SD image -- much like ESPNHD when they broadcast a program in SD.
It looks like Dish picks up all the Canadian broadcasts in SD and after Dish compresses them further, the PQ is terrible. The Canadian broadcasts always seem to have worse SD than most of the U.S. SD broadcasts.
In any event, there is an extreme range in PQ for SD CI broadcasts and the Canadian SD PQ is always at the low end.