I'd love to be wrong but, IMO legal action by way of international arbitration is far too slow a process to assist in any negotiations for KRY.
KRY and Exxon are in vastly different positions economically. Exxon can afford to spend decades in litigation (Valdez anyone) Moreover, Exxon has the benefit of gaining some bargaining leverage with other countries through legal action.
My point is that KRY can't win by bullying and legal action, and needs to focus on getting Sanz and Hugo to sign off on the permit and get going on building the mine.
And as far as the futility of speculating over what would happen in an arbitration, probably best taken to the OT board to make room for more near term information and discussion here.