So my understanding of BigGrecian's post is that provided that it is done under the auspices of an instructor solo flight at night in the US on a piggy back licence is possible without a JAR night qualification.
However surely that doesn't change the fact that that once you have done the training you still need to have the 'Day Only' restriction removed from your JAR PPL until you can act as PIC at night in the US without an instructor's authorisation to fly solo.