This sounds suspiciously like an urban myth.
It may derive from the fact that European insurance legislation insists that all policies cover a driver to at least the mimimum required by law in any EU country they happen to be driving in.
Consequently if somebody nipped over to Paris and had an accident at the ADT they might have found that they were only covered 3rd party (they were only coverred 3rd party anywhere in France of course).
it's certainly not mentioned here:
http://www.discover-paris.info/france_driving. htm
or here:
http://www.bbc.co.uk/dna/h2g2/A190009
and I've never seen it called out in any policy I've held
Can you find it documented anywhere?
Incidently what's wrong with this picture?
http://maps.google.com/?ie=UTF8&z=18&ll=48.873 755,2.295091&spn=0.00223,0.003712&t=k&om=1