After checking the Alameda County Assessor’s property database and the City of Oakland’s city-owned property list, I’ve come to the somewhat educated conclusion that most of the target property is not owned by the Joint Powers Authority or any other public entity.
The only part that is owned by the JPA is the overflow lot southeast of the drainage channel that runs along the southern border of the Coliseum complex. Below is a photo with that parcel highlighted (in green):
The land is about 8.5 acres and is mostly unimproved. Electrical transmission lines run through it, posing challenges to the JPA and developers. How do the lines get rerouted? Who pays for it?
The remaining land (17 acres) would have to be purchased by the team or purchased by the JPA and given to the team. My guess is that it would be the latter. Additional cost of land? $10-15 million, based on the price of the land at Hegenberger Gateway.
By the way, 8.5 acres is not enough space to build a new ballpark in the modern era. 12-15 acres minimum is required. SBC Park sits on a 13 acre footprint.