In the 25 years I worked as a firefighter... I worked basically every Christmas and Thanksgiving. When I wasn't scheduled to work there was almost always a trade or overtime opportunity. And we celebrated our holiday on which ever day was convenient. No one considered it to be much of a hardship that I am aware of.
Hubby did 33 years. If he was scheduled to work a holiday we just left it at that and celebrated on a different day. Yeah, a lot of the younger guys with no families would always take the OT pay to let someone who requested off off. There was always someone who wanted to work. Of course hubby worked for KCFD, a really large department.