Shane - Sirius doesn't offer a 24/7 hockey talk channel anymore (at least according to their website.....I dropped Sirius months ago). XM says that they will offer a 24/7 NHL talk channel.
Cresent -
1. Yes, NHL games will be on Sirius and XM until the 07-08 season. At that time, XM's deal with the NHL becomes an exclusive deal.
2. XM claims "more than 1,000" games will be broadcast on XM. It could mean all, but I figure if they were doing all...they would have said it.
3. Same as above. Sirius has 3 stations dedicated towards hockey play-by-play (typically). If XM uses the baseball stations for NHL hockey in baseball's offseason, then they will have access to 15 channels. But nobody knows for sure yet. Sirius claims they show "up to 40 games a week" while XM claims to show "over 1,000 games a year".
- I'm not sure if you are made a mistake by saying that Sirius covers baseball, or if you were trying to say the NFL, but both Sirius and XM respectively cover all games of the NFL and MLB.
4. Most likely. There probably won't be any discrepancies between the American and Canadian services. Both CSR (XM's Canadian company) and Sirius Canada do need to add additional channels that are "Canadian", meaning music channels dedicated to Canadian artists, or Canadian talk channels, or whatever. Everybody will get these changes. I think it would be too hard to make each service different from each other.
Hope that helps.