Hmmm sounds like their pricing and setup just helped create an ongoing black market.
We'll never really know how many Canadian's are actually subscribed to the US service though because of the fact that US addresses are given during the sign up for service.
When the Sirius NASCAR Radio went live in Sept 06 (it was all Sirius Speedway all the time) I cancelled Sirius Canada when they said the channel wouldn't be available until Jan 07. I waited about a week and signed up with Sirius US.