Its hard to call the store or apple online and ask them "will the ebay stuff work?" since they will try to convince you not to buy from ebay but their retail store with their blah blah story. Anyone outside of US bought applecare from ebay US seller ?
I got my Macbook from the online Canada store, and my Applecare off eBay. No problems at all registering it. Even called up Apple to make sure it was registered (and it is).