TQ,
Don’t know exactly your situation, but I understand the situation: having JAR ATPL and flying abroad. Well, from what I know your JAR ATPL can be renewed, or prolonged, based on your FAA ATP, provided you submit the details of your FAA ATP and associated OPC and LPC checks, not sure about the last one. However; what I did; sent the copy of the new ATPL, issued by non JAR state, copy of the type rating certificate, OPC and a copy of crew member certificate with the letter. What the local authority will do is, they will prolong your license, based on foreign one with the endorsement, “A/C only valid for flights operator name”.
Cheers.