Gov. Code, § 56125

If any reorganization provides for the formation of any new district or districts, the district or districts shall be deemed to have been formed upon compliance with the procedure and provisions of this division relating to reorganization. If the terms and conditions of any change of organization or reorganization provide for the formation of an improvement district or for the annexation of territory to, or detachment of territory from, an existing improvement district, that formation, annexation, or detachment shall be deemed to have been completed upon compliance with the procedure and provisions of this division relating to a change of organization or a reorganization. In any proceeding for a change of organization or a reorganization providing for territory to be formed into, or annexed to, or detached from, an improvement district, the clerk of the county or of the district, as the case may be, shall give mailed notice of hearing on the proposed change of organization or reorganization to all landowners owning land within the territory. No further or separate proceedings need be taken for the formation of any improvement district or for the annexation of territory to, or detachment of territory from, the existing improvement district. To that extent only, this division shall govern and provide the exclusive procedure for the formation of any such improvement district or for the annexation of territory to, or detachment of territory from, an existing improvement district and the provisions of the principal act relating to the formation of an improvement district or for the annexation of territory to, or detachment of territory from, an existing improvement district shall have no application.