That seems very far-fetched. For one, you can refuse gifts. Furthermore, I'd assume that the tax is based on fair market value, and if they can't sell the building because no one wants to buy it, doesn't that mean that the market value is $0?
I think it's based on comparable buildings and what they sold for recently.
For any billionaires out there, if you have unwanted buildings or want to punish me with a large tax bill, I will accept the punishment. Call me maybe!