I just read a fascinating article in Azure magazine called The Hope of Marseilles, which explores why of all the French cities with an increase in anti-Semitism, Marseilles is the only one to have successfully got it under control. I learned a lot about French political culture, why Al Gore likes communitarianism (and so do I...hi, Al!) and France doesn't, and how Marseilles' socio-economic integration happened.
There are many reasons why other cities can't blindly replicate the Marseilles model. But there are lessons to be learned, and not only by France.