Although following the privacy link on the sign I then had to download a 29 page document on which the wifi/bluetooth and tracking is only described in detail on page 10.
Main reason given is simply "the legitimate ", around which are claims its being done to track flows of people and travel methods for planning, data is anonymised and also how long it is kept for (standard EU requirements)
All of this is only available in Dutch, not the English version of the site >>