As an example in which パンを食べている can mean "There is bread which has been eaten,"
I've come up with this kind of dialogue.
（状況：医師が看護師に患者が食事を食べたかたずねる）
医師：「患者は食べ物を全部食べましたか？」
看護師：「パンを食べています。でも果物は残しています。」
(situation: The doctor asks the nurse if the patient has eaten the food.)
doctor: Has the patient eaten all the food?
nurse: He has eaten bread, but he has left fruit.
