HI. im no expert but hope this link will helps. alternatively u may wan to check out CFMU site ;
EUROCONTROL Navigation Domain - Home or any experts here.
www.eurocontrol.int/eatm/gallery/content/public/library/NAV_Application_NAVAID_Infrastructure_Strategy_15_MAY_08.pdf
So far only level restrictions I known from flying is when we are RVSM non -compliant. brnav is more a lateral separation issue due certification/equiptment than level restrictions.
just my2cts.