Any employee organization which is not the exclusive representative of certain employees but which desires notice of filing of any certification, severance, decertification or unit modification petition or issuance of notice of hearing, decision or intent to conduct election affecting such employees may file a statement of interest with the regional office. Such statement shall be in writing and shall include a list of the employment classes which the employee organization has an interest in representing, including schematic codes and class codes as defined in “Pay Scales in California State Civil Service.” The filing shall remain valid for 12 months and may be renewed in writing thereafter.