A tweet from Councillor Walcott long ago pegged that property value loss at $200M; and considering the point he was trying to make we can probably take that as the absolute high end.
Proving this loss and getting compensated for it is a whole other matter. I'm sure the finances would be complicated, but I'd love to see the city be aggressive here and fund a CMLC division for commercial property management+acquisitions+sales. Make fair offers on these properties that kill any argument of loss if refused. If accepted, we can manage the properties until it makes sense to resell them. Decent chance of turning a profit, but even if it doesn't, there is a lot of value in having control where/when its needed.
I'm sure that opens a big can of worms, but I say let them/us eat worms.