In order to take advantage of economies of scale, or in solidarity behind a single cause, it is sometimes advantageous for multiple governmental units to temporarily merge certain aspects of their operations known as interlocal agreements. These are legally mandated and require that certain measures take place involving the Department for Local Government or Attorney General's Office (depending on what kind of agreement is made) before the agreement is recognized. Each agreement should lay out the duration of the agreement, the characteristics of any separate authority created, the financial accommodations, details of how the agreement might be terminated, and the authority within the agreement if a separate authority is not established.
Interlocal agreements can be created between a number of governmental units such as cities, counties, school boards, state agencies, etc. They can be formed to share revenues, work on a project that benefits both entities (e.g. utilities, streets and roads, regional tax incentives, etc), establish joint planning efforts, or any other effort that would benefit both more than either would benefit from the efforts separately.