There are no more Olympic 732s in service. Actually I'm surprised you still saw one at Athens' (new) airport. As far as I know, most should be parked at Athen's old airport or have possibly been broken up there already.
I confirm that there is at least one OA's B732 parked at ATH-Elefterios Venizelos Airport.
I saw it while taxiing last week, and it didn't seem to be used for fire training.
I didn't see its registration.