Mich. Comp. Laws § 123.341
Unless otherwise provided by contract, all revenues subject to apportionment and all outstanding indebtedness to be separately refunded or assumed by the several public corporations shall be divided in proportion to the net revenues received during the preceding fiscal year from services rendered by the system to property within the respective boundaries of such public corporations. All properties, including buildings, shops, garages, warehouses having a permanent location, shall upon appraisal be purchased by the public corporation within whose boundaries it is located for a percentage of the appraised value, applicable to the division of revenues as herein provided, but so far as necessary to the efficient operation of parts of the system lying within the boundaries of another public corporation, such property may continue to be used for that purpose for a charge to such other public corporation for its proportion of the expenses of operation and repairs. Any cash assets and intangible property shall be divided in the same proportion as herein provided for the net revenues.
MCL 123.341