JAR BOY,
For JAA, from CAA licencing department, ref LASORS 2005:
...."In order to satisfy the theoretical knowledge requirements for the JAR-FCL ATPL(H), the holder of a JAR-FCL ATPL(A), or CPL(A) with valid ATPL(A) theory credit, is required to complete bridge instruction for the subjects/topics detailed in Appendix 1 to JAR-FCL 2.050. In addition, a pass in the following ATPL(H) examinations must be obtained, in accordance with JAR-FCL 2.490:- Performance: Operational Procedures: Principles of Flight (H) and the Composite ATPL(H) bridge examination"....
I have just bridged from JAR ATPL(H) to (A),
Hope that helps,
Rotorcraft