I think you need to:
1. Create sql dump file of your osqa database.
2. Write a script or Q2A plugin that convert data from osqa dump file into Q2A .sql dump file structure.
(If you decide to make a script, please share with the community).
Or do the conversion manually, line by line.
None the less, before doing this, you must check if you can retrieve all necessary data from your OSQA database.
Tip: you can do the backup of some existing Q2A instance to lookup how .sql file should look like.