Hi Charley,
Sorry, I haven't got a written reference for that. I was told by a UK CAA inspector that this was so.
The difference between JAA and EASA is that JAA was just an agreement between countries to make the rules the same, therefore a Belgian JAA license was still a Belgian license. But under EASA they are all EASA licenses and therefore the fact that it was issued in Belgium is irrelevant, it is also a French or German license.
Of course all academic for most Bizjet ops as the owner will usually want to be able to fly outside the EASA region if he needs to without having to go and find a different crew.