Winshear Gold (the Canadians) had a claim against Tanzania just...

Winshear Gold (the Canadians) had a claim against Tanzania just in the initial phase. yet to be considered by ICSID. And settling at ~ $30M USD for ~ $90M USD claim ($124M CAD) means that they possibly didn't expected to be fully awarded that amount, didn't have litigation financing, or just needed the money sooner rather than later.

Indiana has been awarded compensation by the court, Tanzania has been ordered to pay. There's nothing to negotiate about that.

The only remaining risk is that Tanzania claim for annulment succeeds. There's very small chance that can happen, but that's still a chance. So the only possible out-of-court settlement could be if Indiana (and their lawyers) see the risk of annulment high enough to justify settling for the smaller amount before committee decides.

IMHO that is not likely, so the only realistic thing to discuss with Tanzania is their payment plan. E.g. give them some concessions (slight discount on total amount, or interest charged) if they are not going to drag this around, and pay with cash rather than forcing Indiana to seek seizing their property around the world (like it was the case when Swedish company won the similar case against Tanzania - with Tanzanians ultimately paying up to get their airplane back).