My limited understanding - there are two scenarios at work:
1) eddy current loss due to Faraday's law, similar to having the first turn of a transformer. As it's a low frequency (50Hz), large size of winding, tiny size of core, and less than 1 turn I believe this will be barely perceptible. In fact the parameters are all the opposite of how you design a decent transformer.
2) If two conductor's pass through the same sheet then the magnetic fields at 90 degrees are working in opposite directions, rotating back and forth with each wave cycle of AC. My understanding is that it's the friction of the two opposing rapidly rotating magnetic fields that that generates heat. Think of it like two circular saws attacking the lump of metal on on opposite sides.
In this example only one core actually passes through the sheet, so I'm struggling to imagine that anything would happen here at all. And as above it may be a non-ferrous plate anyway.
So I'd be inclined to agree that you'd wait forever for something exciting to happen due to that design.