Are you talking old CAA-PPL, or CAA issued JAA-PPL?
If you have a CAA issued JAA-PPL, the CAA will only accept a JAA medical for it, ie. a JAA-FCL 3 certified Class 2 Medical. For an old style CAA-PPL, I have no idea.....
See this thread :
http://www.pprune.org/forums/showthread.php?t=247716
Regards - And best of luck with it, SD..
PS, even if you phone them (CAA) and ask, they may change their minds later....