(a) The powers given by this Article shall not be exercised to deprive the owner of any existing property of its use or maintenance for the purpose to which it is then lawfully devoted.
     (b) The powers given by this Article shall not be exercised to impose regulations or require permits with respect to land used or to be used for agricultural purposes or with respect to the erection, maintenance, repair, alteration, remodeling, or extension of buildings or structures used or to be used for agricultural purposes upon that land, except that buildings or structures for agricultural purposes may be required to conform to building or set back lines. “Agricultural purposes” include, without limitation, the growing, developing, processing, conditioning, or selling of hybrid seed corn, seed beans, seed oats, or other farm seeds.
     (c) The powers given by this Article do not include the right to specify or regulate the type or location of any poles, towers, wires, cables, conduit, vaults, laterals, pipes, mains, valves, or any other similar distributing equipment of a public utility as defined in the Public Utilities Act.