a. Filing offices. Except as otherwise provided in subsection (b), if the local law of the Commonwealth governs perfection of a security interest or agricultural lien, the office in which to file a financing statement to perfect the security interest or agricultural lien is:
1. the office designated for the filing or recording of a record of a mortgage on the related real property, if:
A. the collateral is as-extracted collateral or timber to be cut; or
B. the financing statement is filed as a fixture filing and the collateral is goods that are or are to become fixtures; or
2. the office of the State Corporation Commission or any office duly authorized by it, in all other cases, including a case in which the collateral is goods that are or are to become fixtures and the financing statement is not filed as a fixture filing.
b. Filing office for transmitting utilities. The office in which to file a financing statement to perfect a security interest in collateral, including fixtures, of a transmitting utility is the office of the State Corporation Commission. The financing statement also constitutes a fixture filing as to the collateral indicated in the financing statement which is or is to become fixtures.