Christmas and war mix fine. We all have smart phones. Hop on once for 10 minutes while you are taking your after dinner crap and all will be fine and well.
As for Christmas truce, if both sides agree I say why not? HOWEVER, it is situational. If you declared and someone, and then ask them for truce I think you are an idiot. You should have realized the war was going to cover christmas. If you are destroying the defender, he will probably agree, and you are a nice guy I suppose. But, if you declared and are now getting a beating, there's a good chance that your Christmas truce request will be laughed at. (I'm talking to you SuperCoolYellow). I think it is always fair for the defender to ask for truce.
Maybe I am silly. Maybe I am overthinking it.