I think their plan is to drip feed 500 or so flats onto the market each year over 4 years, in an attempt to avoid flooding the market. But if there aren’t that many buyers they can end up sitting on empty properties like the banks have during the crash, so they’ll probably hold off building all the blocks until they have a better understanding of the market.
I agree with your questioning of who will buy them though. The flats may be state of the art, central and overlooking the river, but the immediate surroundings are pretty average blocks built about 50 years ago. It certainly isn’t a prime area but I can’t see them marketing the flats for less than €3,500/m2 , and when you can pick up houses in prime areas like Pozuelo and La Moraleja for €500k, one wonders why anyone would buy one of these.