My tickets for Gamescom came with free public transport tickets. While the Gamescom website reasonably clearly explains where they can be used, I failed to find if the train I have to take is of the type that has a supplementary charge or not. It is an ICE train, which the Gamescom website says should have this charge, but the Deutsche Bahn website shows nothing like it when trying to book a ticket.
The train I'm particularly interested interested in is the train from Düsseldorf Hbf to Köln Messe/Deutz (ICE 723, says Google maps).