A river authority operating a steam generating plant on or before January 1, 1999, may acquire, finance, construct, rebuild, repower, and use new or existing power plants, equipment, transmission lines, or other assets to sell electricity exclusively at wholesale to:
(1) a purchaser in San Saba, Llano, Burnet, Travis, Bastrop, Blanco, Colorado, or Fayette County; or
(2) a purchaser in an area served by the river authority on January 1, 1975.