"You can take bicycles on board an ICE train as long as they are folded away in a bike bag.
If you’d like to take a bike that doesn’t fold away, you may want to consider the luggage courier service. Your bike will be delivered to your destination for a charge of (currently) €25.80."
Does this mean you can take a standard bike but it just has to be packed in a bag or that the bike must also fold, like a Bike Friday, Dahon, S&S coupled frame or similar? If it requires a true folding bike, just having the bag won't be enough.