Instead CUU has to go to Teck, unless pre-empted by Teck, with a concrete offer from another company to buy CUU's 25% and Teck has the right to match it. If Teck then does not match it, the FROO clause has been exercised and CUU is free to choose Teck's new partner for them. Anyone?

No, CUU offers a deal to Teck and they decide whether to accept it. If they turn it down, CUU has six months in which to sell the same deal, or a better one to someone else. If CUU finds someone willing to take the original deal, with all the clauses, then they can sell it to them and Teck has lost their right to purchase.

The benefit is that once it has been turned down someone else can buy our share of SC without the threat that Teck will step in and take it at the last moment. With a first right of refusal that is what could happen.