California Code, Streets and Highways Code - SHC § 820.5

The department may enter into agreements with authorized officials of the United States for the performance of street or highway construction, improvement, or maintenance projects, including the acquisition of necessary rights-of-way therefor, for military, naval, access, and tactical highways, including highways providing access to timber or other natural resources, regardless of whether or not such highways are on the state highway system. As to any project not on the state highway system, such agreement shall provide for full reimbursement to the department, except for general administrative and administrative engineering expenses.

As to any such street or highway, the department and the commission are, and each of them is, authorized to do any and all things in connection therewith as may be done with reference to the state highways. The commission may adopt resolutions authorizing condemnation of property necessary for such highways with like effect as it may with reference to state highways. All provisions of this article shall apply to any work done by the department under any such agreement.

If desired by the United States, title to any real property, or interest therein, acquired by the department in connection with any such street or highway which is not a part of the state highway system may be transferred to the United States, or any agency thereof, by a conveyance executed on behalf of the State of California by the director. Such conveyance shall only be made in the event the state has been fully reimbursed for any expenditures made in connection with the acquisition of such property or interest therein. Upon completion of the construction of any such highway which is not a state highway, it shall forthwith be turned over to the United States for maintenance and control, if the United States will accept the highway. If the United States will not accept the maintenance and control thereof, such highway shall become a city street or county highway, as the case may be, upon the passage by the commission of a resolution to that effect.

The department may enter into like agreements with authorized officials of the United States to furnish other engineering services, such as laboratory services, upon the condition that the state shall be reimbursed in full therefor.