Someone posted on the flyer web site about this, and it appears you can indeed fly at night on an FAA ticket. I just can't be bothered to find it ot the reasons behind it. Anyway I can, and I have no JAA NQ, because I hold an FAA IR and AM allowed to fly at night and IAW IFR....
In fact, my mate is picking me up in his N reg, and we're going to fly the good old European airways, without holding a JAA IR between us. We may even do it at night, just because we can......