Hi,
Actually it is a good question. AMM says that: "An aircraft in heavy maintenance (e.g. scheduled check, working party or repair after an incident) is not in parked or stored condition. It is necessary to define and apply an adapted preservation procedure." It is quite an obscure wording.
So it seems like it is up to operators CAMO to define and apply this adapted preservation procedure.
I will be glad if someone can share more detailed information on this topic.