I randomly noticed the new channels last night as well. My box (Blue Curve Xi6) has always connected to the TV at 2160p (4K), but of course the broadcasts were never more than 1080p. I am interested to see if I can notice the difference. I am also interested if the cloud PVR will record content in 4K and if so, will it still fill my capacity by the hour despite 4K using so much more bandwidth.
I have tried some 4K/UHD content on Amazon, and I was briefly subscribed to the 4K Netflix tier. The resolution difference was only slightly noticeable to me, but the improved dynamic range (shadows, colours, etc.) was definitely better. Screen size and distance from TV are factors too.
The first 4K broadcast on TSN is the Alouettes vs. the Argos tonight at 5:30 MT. Here is TSN's schedule, that ends today but will no doubt be updated:
https://www.tsn.ca/tsn-4k-broadcast-schedule-1.900579
Sportsnet doesn't appear to publish a 4K broadcast schedule, but hopefully some of the national Flames games are offered in 4K.