Sorry to disappoint, but the Christmas train is not the steam train (or at least not in the past).
The schedules always change at the last minute. However, if you are planning on going to one of the events, I would get there well ahead of time - it's very popular. You can call the 1-800 info line to get an update on the day of the event you have chosen. Last year, they were late coming out of Montreal for Smiths Falls, and the show was delayed by several hours.
It is lots of fun to watch the train go by at a crossing, or somewhere you can get a good look at it. I waited with my 4 year old last year. She was in her PJ's and we listened to Christmas music while waiting at a level crossing in the middle of nowhere. The train runs with Christmas lights lit all the time, so it was a great scene at 10:30pm witha bit of snow coming down...
Andrew