25.—(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 21(4), or during a period of 12 months after the commencement of regular revenue-earning bus operations using the guided busways 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 and 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 of the 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 during the construction of a specified work by the undertaker, Network Rail gives notice to the undertaker that Network Rail desires itself to construct that part of the specified work which in the opinion of the engineer is endangering the stability of railway property or the safe operation of traffic on the railways of Network Rail then, if the undertaker desires that part of the specified work to be constructed, Network Rail shall assume the construction of that specified work and the undertaker shall, notwithstanding any such approval of specified work under paragraph 21(3), shall pay to Network Rail all reasonable expenses to which Network Rail may be put and compensation for any loss which it may suffer by reason of the execution by Network Rail of that specified work.