my son was there for both Thanksgiving and christmas, they had the day off and a decent [sh] meal that was IT, no going out off base nothing, other than he did get to call home twice that day.
Just tell your recruiter you don't want to leave until after christmas. Once youre at your duty station youll get leave during major holidays or when ever you put in a request form and it gets approved
you stay, if you were in tech school you would get a Christmas exodus but in BMT you continue your training. The chow is pretty good over the holidays though and you do get to hang out and watch some movies... Unless you're in fpcon charlie and walking perimeter guard duty around the squad....