Except as otherwise provided in this title, Title 6, Subtitle 4 or 5 of the Education Article, Title 16, Subtitle 7 of the Education Article, or Title 3 of the State Personnel and Pensions Article, the Board shall determine the appropriateness of each bargaining unit. If there is no dispute about the appropriateness of the establishment of the bargaining unit, the Board shall issue an order defining an appropriate bargaining unit. If there is a dispute about the appropriateness of the establishment of the bargaining unit, the Board shall: conduct a hearing; and issue an order defining an appropriate bargaining unit. If the appropriate bargaining unit as determined by the Board differs from the bargaining unit described in the petition, the Board may: dismiss the petition; or direct an election in the appropriate bargaining unit if at least 30% of the signatures included in the petition are of employees in the appropriate bargaining unit. A bargaining unit may consist only of public employees.