Hello,
it's possible and easy.. Just create a modified Initial Load job. Initial Load reads data from target system to IdM storing the data to temp tables..
Basically:
1) Create the AS Java repository if it doesn't already exist (plus create the technical user to UME for the IdM-connection)
2) Create the Initial Load job from NW AS Java template for that repository
3) Delete all the passes from the job that writes anything to Id Store (the data remains in temp-tables)
4) Add a pass that extracts the groups/users to CSV.
regards, Tero