I just don't see where this willingness to offer Corbyn a hand is supposed to come from. As you you point out, there just is no appetite on the part of the Council to offer anything Corbyn would want. And at that point he has about as much leverage as Greece had unless the Tories stock a lot of cans.
I'm also convinced that our great leaders feel less need to offer any nod towards participatory democracy than at most any point in the last few years. For one they are happy to have the far-right occupy the EU critical discourse. I wouldn't call it a conspiracy, more an effect of the Western media system being tightly coupled and in a siege mood, but the result is the same. Reasonable criticism is drowned by right wing lunatics. Then, both the Trump election and the Brexit vote have brought out the latent loathing of democracy in a lot of the professional classes. It is very noticeable among the gaggle of Clinton diehards and on Remain Twitter.
Though I hasten to add that I don't mean the unwillingness to accept the referendum result or whatever.