Nothing contained in this act shall be construed as repealing any existing law nor as affecting any mental health center or facilities for people with intellectual disability established by any county under any other law prior to the effective date of this act except as herein otherwise specifically provided; but no county which has heretofore established or shall hereafter establish under any other law a mental health center or facilities for people with intellectual disability shall make a tax levy under such other law for a mental health center or facilities for people with intellectual disability if it shall establish either singly or jointly a mental health center under the provisions of this act.