Of course they will know in advance where the max will be flying because to start off with they will not have engineering coverage in all locations to cover the new aircraft as they will be very different to the 800's from an engine perspective and other variables. The small matter of a different config in the cabin, seat maps, purchasing allocated seating etc... They will have to deal with upgrading and downgrading aircraft the same as any other mixed fleet airline but they will build a schedule with the max's flying on specific routes at set times. To say they won't know what the plan is beforehand is a complete and utter lie.