Can an arbitrator remain seized of the matter?

In Jackson v. Ontario Power Generation Inc., [2002] O.J. No. 1972, the employee had been dismissed for cause. He grieved his dismissal and as a result, an agreement was entered into which provided for his resignation. The Minutes of Settlement contained a clause that any dispute stemming from the agreement or alleged violation of the agreement would be determined by an arbitrator who remained seized of the matter. The former employee had been barred from the premises but subsequently had employment which required his attendance at the Ontario Power Generation site. His new employers received information from his former employers which led to the cancellation of his employment contract. He then sued for breach of contract. The defendants moved to dismiss his action on the basis that the arbitrator specifically remained seized.