In any case where the department takes over any property or properties which are under lease, contract, or concession, or where the department has heretofore entered into any contract or negotiation or received any bid for any of the purposes set forth in this chapter, the department is authorized to continue in effect and carry out any such contract, lease, or concession or complete any such negotiation or accept any such bid or any modification of any of them which appears advantageous to the department without regard to any limitations or directions as to the manner thereof contained in this chapter. However, this section shall not be construed as requiring the department so to act, but this section is permissive only and then only in respect to contracts, leases, concessions, negotiations, or bids existing, entered into, or received prior to April 1, 1949.