(a) A public procurement unit that is governed by this article may either participate in, sponsor, conduct, or administer a cooperative purchasing agreement for the procurement of any supplies or services, other than voice or data wireless communications services, with one or more public procurement units in accordance with an agreement entered into between the participants. The cooperative purchasing agreement may include joint or multi-party contracts between public procurement units and open-ended public procurement unit contracts that are made available to other public procurement units.
(b) All cooperative purchasing conducted under this division shall be through contracts awarded using source selection methods substantially equivalent to those specified in Division 3.