We chose to take the over night train from Dusseldorf to Alessandria
For our 2010 trip to Tuscany on the 1200GS, booked in January through the web site for early May travel, I think the return cost for the two of us with the bike was £750 including paying extra for having a sleeper compartment to ourselves.
The GS was fitted with a GSA screen and with the screen dropped down went on to the train fine however I still have the scratches on the top of my then new lid from the overhead steel deck.
We found the service to be very good, loading and off loading was very efficient as you would expect with a German service.
We decided on Andermatt and Lake Como for 2011, I priced various ways to travel including the overnight train again but with the distance from Calais to Düsseldorf and the cost in both time and £, and the fact that I hate motorway riding we decided to take the bike down in a rental van, the van we used was only slightly larger than a large people carrier, plenty of cheap rental deals to be had, slightly more expensive through the Euro-pipe, fuel consumption/ cost equated to £70 extra over the 2000 miles, we could share the driving carry both winter and summer riding gear plenty of room for any amount of luggage everything kept dry, no tyre ware or increase of miles on the bike, no worries if the van broke down all covered by the rental, I used the van as a garage for security every night in Italy.
We are going to use the same format again this summer it worked so well for us, planning to go the Black Forest and the Austrian Alps.
Good luck with your trip