The cases of fraternizations between French/British soldiers and German soldiers on the Western fronts are often mentioned, but was there any such case on the Eastern front? I imagine the difference in calendar could make this more complicated, seeing as for the Russians it wouldn't be Christmas for two more weeks.
I'm also thinking of the 2005 film "Joyeux Noël", about such a (fictionalized) fraternization on the Western front. At the beginning, the German soldiers are shown receiving Christmas trees sent by the Kaiser, and them putting them outside the trenches is one of the events that kicks off the truce. Did the Kaiser really had Christmas trees sent to the whole front? If so, what was the reaction of soldiers to this gesture? I can imagine that, as nice as it might look, they would have enjoyed additional food more.
I answered your question about the Eastern Front just the other day here.
The short version is that the Russians privileged Easter over Christmas and, despite the difference in calendars, there is one known case of fraternisation taking place between Russian and Austro-Hungarian troops at Easter 1916.
With regard to Christmas trees - the tree was very much more a German custom than an allied one in 1914. But I have seen no source suggesting the Kaiser gifted large numbers to his troops in 1914 and there are all sorts of logistical reasons why it would have been a hard thing for him to do, One source, Joe Perry, Christmas in Germany: A Cultural History, p.93, describes the trees that undoubtedly were erected in the German trenches at Christmas 1914 as "evidently makeshift".