A beautiful gallery of photos of Christmas in Iran is here:
We can also deduce from such things as Christmas trees being sold on Tehran sidewalks and big Merry Christmas signs hanging in Tehran stores that while American aggression in Iraq may have had the tragic "blowback" effect of driving out 90% of all Christians who once lived there, Muslim tolerance towards Christians is still alive and well in Iran.
Yes, there are christians celebrating Christmas in Iran. If you are spending the holidays with any "bomb Iran" wingnut relatives, you may want to show them this.
Added: found via Libby at http://cernigsnewshog.blogspot.com/