California Code, Public Utilities Code - PUC § 50075.5

All new intercity, interregional, and rural services provided outside the Stockton Metropolitan Area shall be subject to open competitive bidding at least once every five years. For the bidding, the district may be one of the bidders. The district shall cause notice inviting bids to be published at least once in a newspaper of general circulation within San Joaquin County, which publication shall be made at least 10 days before bids are to be received. The contract for service shall be let to the lowest responsible bidder. The board may reject any and all bids and may readvertise in its discretion.