Is a mortgage agreement binding an original mortgagor to a renewal executed by the owner of the equity of redemption?

I find the reasoning in Laurentian Bank v. Weingarten compelling. Otherwise, to bind an original mortgagor to a renewal executed by the owner of the equity of redemption, without notice to or consent of the original mortgagor, would have the practical effect of endowing the owner of the equity of redemption (who may be an entire stranger to the mortgagor and several transfers removed from him or her) with a power of attorney to enter into a new mortgage agreement on his or her behalf. If that be the substance of the agreement, clear language would be required in the original mortgage document to establish it.