We note that these immigrants find jobs in Norway, and that Norway has its own central bank (Norges Bank) and currency (Kroner). I.e. they're not hostage to the ECB's monetary policy.
The level of education in the countries by the Mediterranean is quite high, and at the same time the financial crisis has harmed many young adults who have gone straight from school to unemployment. As a result, the immigrants who come are well educated and prepared for the work force. Many of them also have the labor skills that Norway is in desperate need of, such as engineers and kindergarten teachers.