Cal. Sts. & High. Code § 8707

If the legislative body calls in the original issue of outstanding bonds, it may direct the treasurer to, and the treasurer shall thereupon, advance the maturity of the outstanding bonds bearing interest in the manner provided in Part 11 (commencing with Section 8750), notwithstanding the fact that there may not be surplus moneys in the redemption fund with which to pay the same. New bonds shall be issued in an aggregate amount equal to the total balance of the reassessment unpaid and shall bear interest from their date at the rate fixed by the legislative body.