I don't think this looks to good now, Boris is taking a lot of heat just now with the whole lobbying crisis concerning David Cameron, if this deal goes through its just another example of that.
Perhaps that's the reason for arbitration, so they can green light it and it looks sqeaky clean but it would be so much easier and helpful to Boris if it gets knocked back, he can then stand up in Parliament and inform the world that lobbying doesn't work.