Animated at least used U.S. actors guild for voice work. Luckily, David Kaye had moved to Los Angeles and switched guilds around that time. But Garry, Scott and Co. were and are still members of the Canadian actors guild. Unfortunately, productions are country locked when using guilds so, Animated being a US production, resulted in U.S. actors. I don't think there is anything preventing them from acting together for non contract work, though. Or if you got them all in the same convention for a script reading.