Notwithstanding any other provision of this chapter, if a taxpayer files a notice of intent to rehabilitate and has been rehabilitating an abandoned building continuously for the preceding year and is more than sixty percent complete, then the taxpayer must be allowed to extend the placed in service date until ninety days after completion of construction, provided construction continues diligently until that date. Nothing in this section may be construed to allow a taxpayer to earn a credit allowed by this chapter before the applicable phase or portion of the building site is placed in service.