Chances are it won’t happen. They can set a minimum number of reserves per day and usually Christmas will be right at that minimum or drop below it shortly after pilots are able to drop.

That being said there’s other options. You could swap trips until you can work out something you like. Example: I was scheduled to work Dec 24-27. The 26-27 were above reserve coverage so those days could be dropped so I swapped into a trip that finished Christmas morning at 8:30. 2nd best option if you have to work Christmas.