The term “operative property” means any and all property that is not exempt under this chapter by reason of an election filed under chapter 57-33.2 and which is reasonably necessary for use by any company mentioned in section 57-06-02 exclusively in the operation and conduct of the particular kind of business engaged in by it. Any such property held under a contract for the purchase thereof must be considered for all purposes of taxation as the property of the company holding the same. Any such property, real or personal, held by any company under a rental lease must be assessed by the state board of equalization in the name of such company, if an agreement in writing between the owner thereof and such company is filed with the tax commissioner requesting that such leased property be so assessed. Whenever any property of a public utility company required to be assessed by the state board of equalization under the provisions of this chapter is used partly for operative purposes and partly for other purposes, either by the company or by others, all such property that is not exempt under this chapter by reason of an election filed under chapter 57-33.2 must be assessed by the state board of equalization as operative property of the company. Notwithstanding any other provision of law, all oil or gas pipeline property that is not exempt from ad valorem taxation is subject to assessment by the state board of equalization under this chapter.