The spec refers to fabrication and then shimming - no mention of machining the working surface. The plates will have a fabrication tolerance of more than is being asked for in the survey.
As noted by BStrand the first traffic over it will adjust everything to suit itself (although the weight of the whole train is irrelevant: it ios the axle loading and the weight on the span which is important.
From time to time we have to set track plates for large carousels used to load undersea umbilical cables - typically up to 5000 tonne on a 40 meter diameter. The plates are all set, shimmed and grouted to around 0.2mm. A full load goes on and everything adjusts itself by up to 0.5mm. Big moving things shape their local universe.
This is our team working on a bascule bridge with a laser tracker
