The current proposal from EASA to allow N Reg ops in Europe is that the aircraft must be maintained with European oversight to European standards and that the crews must conform to European licensing in addition to FAA licensing.
This I suspect is to keep the biz jet type operators happy and to give EASA the oversight that they claim is necessary. The cutoff being proposed is 90 days to allow the ferry flight, visitors etc to come and go as needed but ensure that based operators are inside the EASA regime.
Strikes me as being a very reasonable solution to the N Reg issue and as rustle points out holders of an FAA get significant credit towards the JAA IR.
For the record it has not been my experience or that of anyone I know for a CAAFU examiner to try any tricks on candidates. The test is carried out to a standard format identical to the 170a test the candidate already did and is carried out to extremely professional standards. You either make the grade or don't there is no trickery involved.