Just a question,
why wouldn't the city just claim the airspace as 'eminent domain'? what's stopping them?
As I have previously posted, the City has the right to expropriate the airspace at any time. There would be a Hearing of Necessity but the expropriation almost certainly would be approved. According to the law, they have to pay fair market value according to
highest and best use for the land. In the post above, TJ O'Pootertoot suggests the value would not be much because "it's only usable as parkland now". Not true. OP395 designated these lands for future parkland, but was upheld at LPAT without prejudice to the current owner's development application. The City didn't argue that a park was the highest and best use for the land. They argued it was necessary, and that designating the lands for a public park was compliant with planning policy.
The owner of the land did not object to OP395 based on the park use. Their planner agreed that OP395 was one of the permitted uses under the existing secondary plan and planning policies. Their objection was that the City designated the land for a public park but had no concrete plans to acquire the air rights. Private owners can't build a public park, so in order for OP395 to be implemented the City has to acquire the air rights. The panel dismissed the appeal, but did it without prejudice to the developer's private application which will be heard at a 9 week hearing starting this November. If the private appeal is upheld, which it likely will be, the City can still go ahead with Rail Deck Park but they will have to move quickly.
The minute the City initiates expropriation proceedings, there's no turning back. They know they will be exposed to significant financial risk. Their position in the January 2020 staff report suggests they know this and have decided to test the waters with the three acre parcel east of Spadina. They will most likely end up paying a lot for that land but at three acres it won't break the bank. Combined with Oxford's park on the east side of Blue Jays Way, it will give them 7 acres of parkland in that area.