Migrate calendar data from Snow Leo server to Lion server

I have a big problem that doesn't seem to be covered by the migration documentation from Apple. I installed a fresh Lion server on a backup MacMini and I started migrating services. Wiki and OD migrated with some problems that can be solved (links are different in wiki and OD migrated without password because the old configuration was wrong.. but anyway, not these are my problems), but Calendar service (new version, 3) has no Data directory. As far as I can see all "ics" information is now stored in PostgreSQL. Do you have any idea how can I migrate old ics files (from a snow leo server) to this new structure (lion server with postgresql)?

thank you in advance.