I have a bit of paper stuck in the back of my POH that states the installation is approved for both BRNAV and approaches. Was done a couple of years ago.
I was under the impression that when I took part in the GPS trials it had to have this paperwork anyway.
My avionics company did the paperwork and at the time laughingly handed it over saying that it would never be any use to me unless as I flew to the USA in it as there were no GPS approaches in Europe. At least it is worth something now!!!!