(5) In any case where it is established that EMI can only reasonably be prevented by  modifications to Network Rail’s apparatus, Network Rail must not withhold its consent  unreasonably to modifications of Network Rail’s apparatus, but the means of prevention and the  method of their execution must be selected in the reasonable discretion of Network Rail, and in  relation to such modifications paragraph 5(1) has effect subject to this sub-paragraph.  (6) If at any time prior to the completion of the authorised development and regardless of any  measures adopted under sub-paragraph (3), the testing or commissioning of the authorised works  causes EMI then the Authority must immediately upon receipt of notification by Network Rail of  such EMI either in writing or communicated orally (such oral communication to be confirmed in  writing as soon as reasonably practicable after it has been issued) cease to use (or procure the  cessation of use of) the Authority’s apparatus causing such EMI until all measures necessary have  been taken to remedy such EMI by way of modification to the source of such EMI or (in the  circumstances, and subject to the consent, specified in sub-paragraph (5)) to Network Rail’s  apparatus.  (7) In the event of EMI having occurred—  (8) Where Network Rail approves modifications to  Network Rail’s apparatus under  subparagraphs (5) or (6)—  (9) To the extent that it would not otherwise do so, the indemnity referred to in paragraph 15(1)  applies to the costs and expenses reasonably incurred or losses suffered by Network Rail through  the implementation of the provisions of this paragraph (including costs incurred in connection  with the consideration of proposals, approval of plans, supervision and inspection of works and  facilitating access to Network Rail’s apparatus) or in consequence of any EMI to which  subparagraph (6) applies.  (10) For the purpose of paragraph 10(a) any modifications to Network Rail’s apparatus under  this paragraph is to be deemed to be protective works referred to in that paragraph.  (11) In relation to any dispute arising under this paragraph the reference in article 53  (arbitration) to the Institution of Civil Engineers is to be read as a reference to the Institution of  Electrical Engineers.  12. —(1) If at any time after the completion of a specified work, not being a work vested in  Network Rail, Network Rail gives notice to the Authority informing it that the state of  maintenance of any part of the specified work appears to be such as adversely affects the operation  of railway property, the Authority must, on receipt of such notice, take such steps as may be  reasonably necessary to put that specified work in such state of maintenance as not adversely to  affect railway property.  (2) If at any time after the completion of a specified work, being a work vested in Network Rail,  the Authority gives notice to Network Rail informing it that the state of maintenance of the  specified work appears to be such as adversely affects the operation of the authorised tramway  Network Rail must, on receipt of such notice, take such steps as may be reasonably necessary to  put that specified work in such state of maintenance as not adversely to affect the authorised  tramway.  70 (a) the Authority must afford reasonable facilities to Network Rail for access to the  Authority’s apparatus in the investigation of such EMI;  (b) Network Rail must afford reasonable facilities to the Authority for access to Network  Rail’s apparatus in the investigation of such EMI; and  (c) Network Rail must make available to the Authority any additional material information in  its possession reasonably requested by the Authority in respect of Network Rail’s  apparatus or such EMI.  (a) Network Rail must allow the Authority reasonable facilities for the inspection of the  relevant part of Network Rail’s apparatus; and  (b) any modifications to Network Rail’s apparatus approved under those sub-paragraphs  must be carried out and completed by the Authority in accordance with paragraph 6. 