I tried the Chris procedure without success at first. So I do a lot of manipulations (resetting localization, powering off/on the iPod Touch) and suddenly TomTom works ! I tried to lounch Navigon, but then nor Navigon nor TomTom was working.
Now, TomTom works considering that no other applications (Navigon, Meteo,...) are using localization. If TomTom don't receive gps data, I reset Location (see Chris info), lounch TomTom. Then TomTom inform me that he need the authorization for accessing location data, I then go to Parameters/Privacy/Location and I switch ON TomTom Europe (there must be no other application listed otherwise it will not work). Then I switch OFF and ON the iPod on the car kit tool, finally lounch TomTom ... and it is receiving gps data.
There is really a great software problem in the location service of iOS 6. How long to get a patch ?