For the CNL trains after april the 7th it says: CNL40463: München Hbf - Venezia Santa Lucia: Information. Train is not bookable until further notice.
Although it's indeed strange the full fare seems bookable.

I found some information about refunds: http://www.bahn.com/i/view/GBR/en/pr..._tickets.shtml
So for full fare tickets it's: Until 10 days prior to the departure: 25% cancellation fee, minimum EUR 15.00 per seat and night.
From 9 days until the day of departure but before train departure (also applies if customer boards the booked train after 0:00 the following day): 50% cancellation fee, minimum EUR 15.00 per seat and night