I made a booking YOW-YYZ-DXB in J through Emirates' website and I'm wondering if I can choose my seats on the Air Canada flight (YOW-YYZ). In the past I've had to make this booking separately but now I see that it all can be done in one booking through Emirates. Any ideas? Emirates MMB won't let me choose AC flights, and AC MMB doesn't recognize Emirates confirmation.

Thanks.