(a) Subject to subdivision (b), and except as provided in Section 15688, if the trust instrument provides for the trustee’s compensation, the trustee is entitled to be compensated in accordance with the trust instrument.
(b) Upon proper showing, the court may fix or allow greater or lesser compensation than could be allowed under the terms of the trust in any of the following circumstances:
(1) Where the duties of the trustee are substantially different from those contemplated when the trust was created.
(2) Where the compensation in accordance with the terms of the trust would be inequitable or unreasonably low or high.
(3) In extraordinary circumstances calling for equitable relief.
(c) An order fixing or allowing greater or lesser compensation under subdivision (b) applies only prospectively to actions taken in administration of the trust after the order is made.