17. Where, in accordance with the provisions of this Schedule, the promoter affords to the specified undertaker facilities and rights for the construction, use, maintenance and renewal in land of the promoter of alternative apparatus in substitution for apparatus to be removed, those facilities and rights may be granted upon such terms and conditions as may be agreed between the promoter and the specified undertaker or, in default of agreement, determined by arbitration.
18. In determining the terms and conditions mentioned in paragraph 17 in respect of alternative apparatus to be constructed across or along the authorised works the arbitrator must—
(a)give effect to all reasonable requirements of the promoter for ensuring the safety of the authorised works and for securing any subsequent alterations or adaptations of the alternative apparatus which may be required to prevent interference with any such works; and
(b)so far as it may be reasonable and practicable to do so in the circumstances of the case, give effect to any terms and conditions applicable to the apparatus (if any) constructed across or along the authorised works for which the alternative apparatus is to be substituted and to any other reasonable requirements of the specified undertaker.
19. If the facilities and rights to be afforded by the promoter in respect of any alternative apparatus under paragraph 17 and the terms and conditions subject to which those facilities and rights are to be granted are, in the opinion of the arbitrator, more or less favourable on the whole to the specified undertaker than the facilities, rights, terms and conditions applying to the apparatus to be removed, the arbitrator must make such provision for the payment of compensation to or by the promoter by or to the specified undertaker in that respect as appears to the arbitrator to be reasonable having regard to all the circumstances of the case.