At the Deutsches Museum Verkehrszentrum, there's an exhibit extolling the virtues of concrete slab trackwork. As I understand it, that was tried on the line between Chicago & St Louis when they were upgrading it for higher-speed passenger running, & failed miserably because freight trains were using the same tracks. Apparently quite a number of the slabs just broke, & all the completed work had to be taken up & relaid with concrete crossties, which really blew up the budget & schedule. Considering that a Superliner is a great deal heavier than the typical European passenger carriage, that looks to me like a decision taken without proper evaluation.