I would imagine that any purchaser of the site will insist on a "no strings attached" sale.
The history of the site points to this.
My theory is that ALL development proposals on the Power Station site have been "Aunt Sallies" with no real intention of completion...and this included the Northern Line Extension one.
The idea,as I see it, has always been to drag the process out until Wandsworth Council finally concede a Dangerous Structure notice,and the site can be cleared and redeveloped tabula rasa.
In the meantime,developers simply sell the site to one another,perhaps turning a decent profit on the basis of speculation and the general rise in land prices.
Each developer produces a "window dressing" scheme,to maintain market interest in what is a very difficult site.The more eye-catching the scheme,the better for them.
Then it's time to play "pass-the-parcel" once again. Its just that this particular developer dropped the parcel.
There'll be plenty more candidates ready to snaffle the freehold up at a bargain price if the developer really does go bust.
And one day,the building literally starts to fall down,the then owner will cry a few crocodile tears and flatten the rest,and go for maximum development,and will laugh all the way to the bank.
Will THEY want to build a tube extension? Don't hold your breath.