CCP §1245.260: (a) If a public entity has adopted a resolution of necessity but has not commenced an eminent domain proceeding to acquire the property within six months after the date of adoption of the resolution,

(a) If a public entity has adopted a resolution of necessity but has not commenced an eminent domain proceeding to acquire the property within six months after the date of adoption of the resolution, or has commenced such proceeding but has not within six months after the commencement of such proceeding attempted diligently to serve the complaint and the summons relating to such proceeding, the property owner may, by an action in inverse condemnation, do either or both of the following: (1) Require the public entity to take the property and pay compensation therefor. (2) Recover damages from the public entity for any interference with the possession and use of the property resulting from adoption of the resolution. Service by mail pursuant to Section 415.30 shall constitute a diligent attempt at service within the meaning of this section. (b) No claim need be presented against a public entity under Part 3 (commencing with Section 900) of Division 3.6 of Title 1 of the Government Code as a prerequisite to commencement or maintenance of an action under subdivision (a), but any such action shall be commenced within one year and six months after the date the public entity adopted the resolution of necessity. (c) A public entity may commence an eminent domain proceeding or rescind a resolution of necessity as a matter of right at any time before the property owner commences an action under this section. If the public entity commences an eminent domain proceeding or rescinds the resolution of necessity before the property owner commences an action under this section, the property owner may not thereafter bring an action under this section. (d) After a property owner has commenced an action under this section, the public entity may rescind the resolution of necessity and abandon the taking of the property only under the same circumstances and subject to the same conditions and consequences as abandonment of an eminent domain proceeding. (e) Commencement of an action under this section does not affect any authority a public entity may have to commence an eminent domain proceeding, take possession of the property pursuant to Article 3 (commencing with Section 1255.410) of Chapter 6, or abandon the eminent domain proceeding. (f) In lieu of bringing an action under subdivision (a) or if the limitations period provided in subdivision (b) has run, the property owner may obtain a writ of mandate to compel the public entity, within such time as the court deems appropriate, to rescind the resolution of necessity or to commence an eminent domain proceeding to acquire the property.