This has happened, for sure. The interesting thing is how it will play out. The rents in a hole like Grimsby are ridiculous, and all the properties are vacant. I remember that a downtown luxury condo was mostly empty.
Cornering means that you have a monopoly on a commodity. It is a billionaires wet dream. Just like diamonds, it is worth it to take rental units out of the market. Then you can choose the rent.
These guys get clean money through rent, but also in price increases. If prices fall, then they might want to get out, and sell to the banks. Rents can become so high as to destroy the economy, and then there are no rents. The big threat to 'cornering' is a huge influx of new units, that they can't buy out.
I'm predicting this will crash like Japan. We are looking at a 50% fall in prices and rents. It's ironic that they are afraid of this happening, and, thus, don't increase interest rates.
ps. local wannabe rich types are thinking of buying from the laundries and just using Airbnb. However, this train has left the station. Everybody and their dog will be doing it, which knocks down the fees, and brings up serious gov't and condo-board involvement.