The exam credits are to qualify for a license, and only licenses can be used to qualify for the issue of another country's license. No exam credits are not transferable.
There is no such animal as a "frozen ATPL" - you only have a CPL, with exam credits. That is - no country issues an ATPL with "frozen until xxx hours achieved" stamped upon it, the term "frozen ATPL" is a slang term used by those unwilling to admit they hold a CPL.