Yes, the JAR-FCL is supposed to make flying in other JAA States easier.... European Harmonisation is was called once! But be careful, not all states have introduced ALL licences.... don't have the list with me, but I think France for example have the fixed wing JAR-FCL but not the helicopter.
Germany recognises, according to the rules, the private JAR-FCL (H) licence, though I would have to check about the commercial regulations. Sure, air law is a bit (quite?) different and not speaking German would be a big handycap. Best bet would be to ask directly at the various companies.... most have homepages, too.
Westy