Every county, except a county in which a metropolitan municipal corporation is performing the public transportation function as of July 1, 1975, is authorized to perform such function in such portions of the unincorporated areas of the county, except within the boundaries of a public transportation benefit area established pursuant to chapter
36.57A RCW, as the county legislative body shall determine and the county shall have those powers as are specified in RCW
36.57.040 with respect to the provision of public transportation as is authorized pursuant to RCW
36.57.040.