Shaw's taken the approach that they don't announce channels until they're actually airing, or at least a sure thing. I think, as DSgamby has said, they don't want to raise expectations that might not be met. Whatever their reason, it is a deliberate strategy on their part.
It's not a matter of customer expectations. Firstly, it's a matter of the competition - they don't wish them to know exactly what they're doing. Secondly, it's a matter of the supplier negotiations - if the supplier knows that you "want" a particular channel or group of channels then the negotiations with the supplier have been compromised putting you, as a provider, in a weaker bargaining position.
With Bell and Discovery Channel (and Space), the latter doesn't apply directly since you're negotiating with yourself to some extent - although I have seen "silos" in a company negotiate harder between themselves than with outsiders (if Measures of Performance are poorly enacted).
Shaw doesn't seem to be too good about communicating previews, specials and offers and such. They have several avenues to reach me: mail, email, website, digital terminal message, but I rarely seem to get information about these items that are of interest to me.