The examiner can only sign for renewal/revalidations of ratings in a licence of his own home State.
Nope. An examiner can sign the renewal/revalidation's of any member state with the prior permission of the appropriate state CAA's. We employ pilots from half a dozen JAA member states and I carry out the LST/LPC on all of them. Also due to the unique types that we operate I am continuously out in Europe doing LPC's on non UK licence holders.