It depends but providers use Variable Bit Rate Encoding, where everything on the transponder is judged at the same time and the encoder decides which channel or the 8 to 14 channels on the transponder gets the most bandwith, and its aways changing based on what kind of action is being shown on the screen.
I have also been doing some work at ESPN, and I can tell you some of the feeds they get in 720p do not always look good. That is out of their control as each truck is different that they use. I remember when ESPN use to have their own fleet now they just rent them.
If your watching DISH on one tv and the same show on DIRECTV on another TV you will notice that sometimes one looks better then the other and vice versa, this is the reason why.