One problem within Star Alliance is you book a codeshare on one partner's web site with another airline and see the booking class, but that booking class is for the ticketing carrier and it does not always correspond to the same booking class with the operating carrier. So you may have booked a UA "V" fare but it mirrors into a "T" fare class with AC. Unfortunately AFAIK there is no way of knowing unless you call the carrier and specifically ask them based on your planned routing.

AC is very good at "screwing" their customers by booking codeshares into the lowest possible fare class of the operating carrier, so it would not come as a shock to me if the same were happening in reverse.