Ind. Code § 8-1-2.3-5

Sec. 5. Effect of Incorporation, Annexation, Consolidation or Merger. After January 1, 1979, the inclusion by incorporation, annexation, consolidation, or merger of any part of the assigned service area of an electricity supplier does not impair or affect the rights of an electricity supplier to continue to solely furnish and extend retail electric service throughout any part of its assigned service area, except as provided in section 6 of this chapter.