Persuaded by precedents from eight states that permit defendants to invoke arbitration agreements between plaintiffs and nonparties based on an “expanded” theory of equitable estoppel, the 10th U.S. Circuit Court of Appeals — citing a contrary decision from the Illinois Appellate Court — predicted the Oklahoma Supreme Court would apply the broad approach “in cases where the signatory plaintiff’s claims either (1) rely on the terms of the written agreement containing the arbitration clause, or (2) raise allegations of …