Input-tax credit availability on ducts and manholes for optical fiber networks affirmed, not barred by immovable-property exclusions. ITC on ducts and manholes used in OFC networks for telecommunication services is not barred by the immovable-property exclusions in section 17(5) of the RGST Act because, under the Explanation to section 17, such ducts and manholes function as part of plant and machinery used to make outward supplies and are not excluded as land, buildings, telecommunication towers or external pipelines.