I was wondering this myself. I got hired for ZDV and used to work at ZDV as an RPO for WCG.
I remember that sometimes, the developmentals would get the holidays off because they follow the WCG instructors schedule which is 0630-1500 M-F and holidays off. However, sometimes the developmentals were required to work the holidays as an A-side. I am not sure if it is like this at the other facilities. I spoke w/ my good friend who as been at ZDV for 5 months now and he told me that I can probably expect to work Thanksgiving, Christmas, and New Year which I expect to arrive at my facility around the second week of NOV.