Someone above mentioned other countries just validate you license. Now that's something different then getting the countries full-license.
If you have a FAA license with enough hours, you can get that license validated here as well. But it's a validation and only valid for 1 year.
There is no real conversion to a JAA license as far CPL, IR and ATPL go. And there lies the problem. But everything will be solved when EASA takes over the licensing and the whole JAA system will be binned.