In French, a "plantation" is a large farm on which crops are raised, often by resident workers, if not slaves. A "Rhum de plantation", only means the rum was distilled on the estate where the sugar cane was grown. So, one can expect to be genuine "rhum agricole". But, since there is not regulation for this "appellation" (designation), it can be anything, of any quality. It's the French equivalent of "Estate Rum" labels.