Currently there is NO way to convert a A&P licence into a JAR 66 licence. I know because there are several American expats working for my company who would like to get their A&P licences converted and I talked to the head of the Irish Aviation Authority Personnel Licencing Department about it. All they can do is to credit the years you worked on aircraft towards your professional experience.
Ok now for myself, I´m a German citizen, but I used to work for a few years in Ireland. During this time I passed the exams for the Irish Basic Aeronautical Engineering Certificates (BAEC) Part 2 (pressurized airframe), Part 4 (gas turbine engines) and Part 6 (Electrics), each with one eassay type written exam and a tough oral exam later. When Ireland joined the JAA my Irish certs got grandfathered into a JAR 66 B1 licence witout a type rating. I moved back to Germany and started working for my current company. We do the contract line maintenance for a big US parcel carrier. When working there I decided that it would be good to have an A&P licence as well, so I sat down studying and later went to Dallas, Texas to do the exams. As I stated above the American carrier we work for requires mechanics to have a type training additionaly to their A&P. I did the courses on B757 and MD
-11. My own company sent me independently from the work on the American planes to a JAA approved B737NG course. A while ago they also decided that to get a FAA company approval, based on a German LBA
approval, which would allow people without an A&P to sign off US MD
-11s, to send me and a colleague (we are the only ones in our station with a JAA licence) to a JAR 147 type rating course with Lufthansa, because the American MD
-11 course was not accepted by the JAA.
The funny thing is that only my colleague and myself are allowed to sign off European registered MD
-11s and under the JAA company approval, but any man and his dog, who has done the American course, can sign off American MD
-11s under the FAA company approval based on the JAA approval.
The company simply wants to use our names for getting the company approval.