My understanding is the same as pewpew. If the domestic segment is part of an international flight its included, but if you need to re-check in for a domestic portion with a connection longer than 24 hours it would be treated as a domestic leg, with luggage fees applied.

That being said, I would print out the information you are posting here. If its from the AC website and linked to your reservation, I cannot see how they could charge you for the baggage fees.