8.—(1) If any alterations or additions, either permanent or temporary, to railway property are reasonably necessary during the construction of a specified work or any protective works under paragraph 4(4), or during a period of 12 months after the commencement of regular revenue-earning train operations using the new railways comprised in any specified work, in consequence of the construction of a specified work, such alterations and additions may be carried out by Network Rail and if Network Rail gives to the undertaker reasonable notice of its intention to carry out such alterations or additions, the undertaker shall pay to Network Rail the reasonable cost of those alterations or additions including, in respect of any such alterations and additions as are to be permanent, a capitalised sum representing the increase in costs which may be expected to be reasonably incurred by Network Rail in maintaining, working and, when necessary, renewing any such alterations or additions.
(2) If the cost of maintaining, working or renewing railway property is reduced in consequence of any such alterations or additions referred to in paragraph 8(1) a capitalised sum representing such saving shall be set off against any sum payable by the undertaker to Network Rail under this paragraph.