(1) If any highway district shall include within its boundaries any incorporated city, or any portion of a city, the power of taxation on the part of the highway district as to ad valorem taxes, and in general all power of taxation or assessment, shall extend to and include the persons and property within the territory of the included city. The residents of the included territory shall be deemed for all purposes residents of the highway district, and entitled to vote at highway district elections to the same extent as other residents of the highway district. Nothing in this title shall be construed as affecting or impairing any power of taxation or assessment for local city highway purposes on the part of the authorities of the city of any included territory. Each incorporated city, or portion of it, within a highway district, shall constitute a separate division of the district. The city council of each incorporated city within the territory of a highway district, so far as relates to their city, shall have the powers and duties as provided by this chapter and as provided in chapter 3, title 50, Idaho Code, in such case.