Saw this on the ParkTrains list. You might want to inquire if heading to California to ride it early next year:

I read on another website that the Disneyland Railroad will be shut
down for refurbishment beginning Jan. 31,2005 thru Mar. 12,2005.
Has anybody else heard this? What kind of work are they planning?
Inquiring annual passholders and railroad lovers want to know.

Bob:

Here's more info...

That is what's reported on the Visions Fantastic refurbishment page:

http://www.visionsfantastic.com/refurbishments.html

That isn't an official Disneyland website though so I don't know where that information came from.  The Disneyland website only lists all the attraction refurbishments through 2004 and it doesn't go into 2005.