Depending on the version, the newer phone manager pro speed dials are stored in the user's My Documents folder (My Documents\Avaya\IP 400\PhoneManager\Profile).
I copied all the files into the new users directory (My Documents\Avaya\IP 400\PhoneManager\Profile) and modified the xml [EXT#].xml to change the username and also the userid.ini to update where the file is stored (may not be necessary).
Also I started Phone Manager first before doing anything and had it create a default profile before overwriting and editing it.
Probably took me about 5 minutes, but I had 5 tabs setup with about 50 users who each had multiple phone numbers.