Interesting. That one diesel HST wasn't very successful. It's been taken out of service again and the line is now operated by a slower train again. This seems to suggest that electric trains are more suitable for high-speed lines, although it's not clear why exactly this diesel train didn't perform the way it should.
It was a 'tilting' train(leaning into the curve). Some part of that mechanism was constructed in wrong ways (too thin), which led to partial cracks, which led to partial derailing, trailing sparks. Which led to investigations of all of them, showing more cracks in development. So they have been "grounded" for a while, conventional trains taking over. Then it was deemed safe to operate them in non-tilting, conventional modes, which led to delays. So Deutsche Bahn wanted their money back, and got it. But no tilting diesel-trains.
