The time limits established by Sections 65950, 65950.1, 65951, and 65952 may be extended once upon mutual written agreement of the project applicant and the public agency for a period not to exceed 90 days from the date of the extension. No other extension, continuance, or waiver of these time limits either by the project applicant or the lead agency shall be permitted, except as provided in this section and Section 65950.1. Failure of the lead agency to act within these time limits may result in the project being deemed approved pursuant to the provisions of subdivision (b) of Section 65956.