Frank,
My wife and I arrived at the same time last year. The train got into St. Jean about 8:30pm. We walked up the main street and a lady directed us to the pilgrim office. It was open.There were two gentlemen keeping the night watch, and they were very kind and helpful. They walked us up the street (just a few doors) to the municipal albergue and got us situated. We were then walked back down the street to a restaurant that was ready to close, but after a few words from our guide, we were served dinner and wine. We were the only people in the albergue. We set off the next morning taking the valley route as advised. It was great. We stopped in Valcarlos (jet lag) and arrived in Roncesvalles the following day. Call ahead (or get help calling ahead) for confirmation that an albergue or pension will be open. Many businesses will be closed from Christmas to January 6th (Feast of the Epiphany), but lodging and food can be found without too much difficulty,just fewer options. We spent Christmas eve in Santo Domingo. You will probably wind up somewhere near there as well. Check our blog (see signature at the end of this post) for more information. We had a great Camino.I know you will as well. Have fun.