I don't think the import / export is working for federated databases even in the context described by @so22: "export a specific database (could be a federation member) which you can then import into a standalone (non-federated) database". The reason
I am telling that is because I tried to export federation instances and be them the root or a federation member, I got the following exception:
Cannot extract a DAC from database DbName because the database has federations. Dac does not support federated databases.
From my point of view, even the possibility to export a federation instance and then restore back a non-federated database would have been useful for backup scenarios. Hopefully this would be possible in a future version.