You can get the HD plus package added to basic cable even though you would be getting stations that are on the tiered line-up. I tried that when I was going to degrade my package down for the time I was in college but decided to stay with full cable.
BTW Yes you can add NHL Center Ice. You can add any extra service it doesn't matter if your a basic or a full cable subscriber. The only thing that's bad is that you won't get the discounted price you'll have to pay the $219.95 I think it is for the season. Then later on if its the same as last year you will be able to order the playoff special for $49.99 like I did last season.
Shaw Gateway + 2 Portals, DCT 6412, DCT 3080, Sony 46' LCD, Sony 32' LCD, XBOX360 Slim, PS3 , Nintendo WII