The taxes imposed by this chapter upon the property of the companies defined in s. 76.02 shall be in lieu of all other taxes on such property necessarily used in the operation of the business of such companies in this state, except that the companies shall be subject to special assessment for local improvements in cities, villages and towns. If a general structure is used in part for operating the business of any company defined in s. 76.02 and in part for nonoperating purposes, that general structure shall be assessed for taxation under this chapter at the percentage of its full market value that fairly measures and represents the extent of its use for operating purposes and the balance shall be subject to local assessment and taxation, except that the entire general structure is subject to special assessments for local improvements. All property not necessarily used in operating the business of any company defined in s. 76.02 is exempted from taxation under this chapter and is subject to local assessment and taxation. The taxes so imposed and paid by such companies shall also be in lieu of all taxes on the shares of stock of such companies owned or held by individuals of this state and such shares of stock in the hands of individuals shall be exempt from further taxation.