The board may deal with and enter into written contracts with the employees of the authority through accredited representatives of such employees or representatives of any labor organization authorized to act for such employees, concerning wages, salaries, hours, and general working conditions. All employees of all classes serving any passenger transportation company at the time of its acquisition by the authority shall continue in their respective positions and at their respective compensations for three months after any such acquisition. Thereafter, the board shall exercise its discretion as to retention of and compensation of employees of all classes; Provided, the terms and conditions of any existing collective-bargaining agreement between any passenger transportation company, acquired by the authority, and its employees shall be recognized and accepted by the board.