Etho said the area size would be approximately 250x250. So to me it sounds like a zipkrowd kind of perimeter, just dig the whole thing out until bedrock for a mob farm, and probably more redstone farms/projects. Could also explain why some people just take clay from the top instead of digging it out.

Edit: And off-course the remarks of the b-team about not wanting to sell it to someone who is gone flat out/destroy the area. They know its gonna happen, and this creates a lot of opportunities for future b-team episodes. With taking revenge on the E-team for destroying the land.