This issue occurs when an object in the XPSImport data already exists in the Policy Store that the new data is being merged with, and is being used for something, in this case, a Legacy Federation configuration.
Simply, the following is observed:
- Object A exists in Policy Store A
- Object A also exists in Policy Store B
- When Policy Store B is exported and merged with Policy Store A, it errors out because Object A already exists and is in use in Policy Store A.