In Citizens Utilities Co. v. Superior Court (1963) 59 Cal. 2d 805, the California Supreme Court refused to apply section 1249, the predecessor to section 1263.120 challenged here, to the valuation of a public utility system that did not compensate the utility for improvements to the system which were required to be made by law. (As stated, ante, the exception was codified in 1975 in section 1263.240 (Stats. 1975, ch. 1275, 2, p. 3450, operative July 1, 1976).) The court stated, "it has been held that section 1249 is not inflexible and does not always apply, even in private condemnations. In Redevelopment Agency v. Maxwell (1961), 193 Cal. App. 2d 414 . . ., it was held that, in spite of the mandate of the section, if the property sought to be condemned were destroyed by fire after summons issued, that fact should be considered by the trier of fact in determination of the award. If involuntary destruction of the property after issuance of summons may be considered in diminution of an award of compensation, in spite of the language of section 1249, it follows that involuntary betterment of the property may and should be considered in assessing the award if the improvements are of use and benefit and add to the value of the property sought to be condemned. Thus, the trial court held, and held properly, that the problem could be solved by simply devising a procedure whereby the value of petitioner's water system would be assessed as of the date of trial rather than the date of summons. Petitioner challenges the power of the trial court to so improvise. The trial court had such power. The provision of the Constitution compelling the payment of just compensation for a public taking of property (Cal. Const., art I, 14 (now 19)) is self-executing. Since this is so it has consistently been held, in inverse condemnation cases, that inherent power is reposed in the trial court to provide for the assessment of just compensation in situations not within the purview of existing statutory provisions. The trial court, in the instant case, was empowered to devise a procedure whereby the value of petitioner's water system could be justly and constitutionally assessed. This it did by providing that in the case of petitioner the condemned property should be assessed not as of the date of the summons, but as of the date of trial. This was a proper exercise of the inherent power of the trial court. It certainly protected petitioner for any increased value to its properties caused by involuntary improvements made after summons and up to the date of trial or of judgment. Inasmuch as the Legislature has failed to provide a procedure to cover the contingency involved, pursuant to its inherent powers the court had the power to devise a proper procedure." (Id. at pp. 811-812.)