Is Air Canada maxing out ACRouge's crew hours because of the MAX grounding?
 

Apparently I am being bumped off my flight from Montreal to Cancun AC1882 on 11th October in fare paid Premium Rouge ticket.
They tried to rebook me to the next day, claiming there's no seat on the flight I had booked, 2 months in advance with seats "confirmed"

They are very reluctant on explaining why, and they still wouldn't tell me exactly why they cannot book me on that flight at all.

"Business Class" tickets are rarely oversold, which makes me wonder and suspect if I were kicked off the flight because of dead-heading flight crew.
I looked it up on ExpertFlyer, my seats 4H and 4K are magically "available" on this sold out flight. (it wouldn't even return any results on expertflyer prior to that).

It took me 3 hours on the phone, spoken to two agents (the first one hang up the phone on me) and finally manage to get myself to Cancun on the same day on a different airlines. Still trying to work out compensations... which i am not too optimistic about.

Why do you think this has anything to do with hours or deadheading crew?

The flight is overbooked, though I'm not sure why or how anyone in J would be affected by that.

As for your seats being "magically available", what do you think would happen if it was booked 26/24 and then you moved off the flight? Your seats would be unoccupied and it would be booked 24/24. That is probably the only thing in your post that has a very obvious answer.

Crew Max-Out's wouldn't happen on the 11th of the month.