I'm actually going to have to disagree with you on this one. There are definitely places where the limitations of the MPEG2 encoding really come through on Shaw -- especially when it comes to macroblocking on fast motion. The TSN SportsCentre intro is the most obvious example that I can think of off the top of my head.
I'll take your word for this as I have no interest whatsoever in sports. However a lot of what Dish Network and DirecTV do, and what Shaw doesn't do, ends up significantly lowering screen resolution. You pick your poison.
While I don't have DirecTV for comparison, I have measured some of the Dish Network HD sports channels running at twice the bit rate as Dish Network HD premium movie channels. Pity
I can understand why they would allocate more bandwidth in this manner, but it does serve to drop their movie channels to absurdly low bit rates and horrible softening.
There are a few twists that come into play. At least on Dish the resolutions of many HD channels are based on non-square pixels - in other words 1440x1080 vs. the 1920x1080 that Shaw runs. This helps lower bit rates and attendant motion distortions for Dish, but it does increase horizontal softening. Furthermore, a number of US sports channels are produced in 720p, not 1080i. Again this helps motion, but hurts overall resolution. From a strict comparison point of view, it's fair to point out that Canadian channel sports feeds of events produced by the US networks likely undergo at least 1-2 extra generations of processing/recompression/rescaling. That can't help. All of these can lead to apples to oranges comparisons. Regardless, the bottom line is how the result appears to you on your screen.
With sports, people tend to tolerate softer pictures over motion artifacts. Unfortunately this is not strictly the case for movies, where a more detailed picture can add a lot to my enjoyment. This is where Shaw has excelled, although they too are dropping bit rates to squeeze in more channels. I will be curious to see what they allocate as they shift to H.264.