Hockey Viewing Confusion

For some reason, the NHL playoff series between the Chicago Blackhawks and the Calgary Flames, which the Blackhawks won last night, 4 games to 2, with a 4-1 win, has almost entirely been televised only on TSN, the Canadian sports cable network, and of course to people with dishes, etc.
Does anyone know why Hockey Night in Canada did not or was unable to pick up the Chicago-Calgary series most, if not all, games? While I enjoyed watching the Anaheim Ducks-San Jose Sharks series (which Anahaim won last night, also 4 games to 2, with a 4-1 win), I like Calgary and Chicago boasts Buffalonian Patrick Kane, so that series would have been more enojoyable for me personally, and it seems in the past that whenever CBC/Hockey Night in Canada had a game involving a Canadian team to show, it would do so without a second thought.
If you are aware of any contractual or other reasons for this, please drop me a line.