Pete,
Congrats on getting an interview with Privatair! Not many people do... I can't help you much with specifics regarding the actual interview, but I can say that you are making the right choice with regard to company. Do you know whether you are being interviewed for the Dusseldorf-EWR service exclusively or for the BBJ charter side? The BBJs are flown worldwide on a charter basis as far as I can tell - that would be very interesting flying indeed!
What specifics have you been given regarding your potential flight regime?
Good luck and keep us informed with your progress!