Cal. Pub. Util. Code § 161023

The department may acquire land or any interest therein for purposes of this division pursuant to procedures applicable to the acquisition of land by the department or the commission. If other means of acquisition have not been successful, the department may exercise the power of eminent domain for these purposes. The power of eminent domain may only be exercised to acquire land which is necessary for construction of the relevant highway route or guideway alignment, and shall not include land for rest stops or other ancillary uses.