When a county public library, city-county public library system or regional public library system shall have been established under this article, any municipality which is aiding in maintaining or supporting a public library, or which desires to aid in providing public library service for that portion of the county’s residents which reside within the municipality, may participate in said county public library, city-county public library system or regional public library system. This participation shall be on such terms as may be agreed upon among the governing body of the municipality, the board of trustees of the existing municipal public library and the board of trustees of the county public library, city-county public library system or regional public library system.