None of us are speculating Snoopster, all three of us have varied experience in the industry to inform our comments.
Neither have I disputed the accounts but you need to understand a hydro station is different to a gas turbine and the difference does not relate to an accounting standard but should be included.
I do wonder though if the depreciation that MEL reports is the same as GNE or is more of an accounting fiction. I haven't looked into it.
As you know I own a windfarm designed for 20 years at which time gearboxes will need replacing. I suspect the towers and footing will prove longer lasting. Presently this is another 20 years when I think the transformers will need replacing or at least a bit of attention.
It all depends on how things are designed operated and maintained as well as the type of plant.