All operating property and all other property that is primarily and directly used in the production, generation, transmission, or delivery of electricity or natural gas subject to replacement tax or transfer replacement tax is exempt from taxation except as otherwise provided by this chapter. This exemption shall not extend to taxes imposed under chapters 437, 438, and 468, taxpayers described in section 437A.8, subsection 6, or facilities or property described in section 437A.6, subsection 1, paragraphs “a” through “f”, and section 437A.7, subsection 3.