Just checked the US store and Canadian store. The US store has two Sirius apps, Sirius XM Premium Online and XM SkyDock. Both are above version 1.0. The Canadian one has a way different icon, and is version 1.0, as you said. No idea why. But the US usually get the good stuff before us; it's a shame.
Still have no idea why it hasn't been updated. Perhaps they don't take their iPhone customers (specifically Canadians) as seriously as they should. Have you tried contacting Sirius? Perhaps there is a new version in the works?