To the presiding officer is delegated the authority to render initial or recommended decisions in all proceedings before him, including motions, petitions and other pleadings. Tentative or final decisions will be rendered by the Administration. The same officers who preside at the reception of evidence pursuant to section 7 of the Administrative Procedure Act shall render the initial or recommended decisions except where such officers become unavailable to the Administration, in which case another Presiding Officer will be designated to make such decision or certify the record to the Administration. Where the Administration requires the entire record in the case to be certified to it for initial decision, the Presiding Officer shall first recommend a decision, except that in rule making:
(a) In lieu thereof the Administration may issue a tentative decision or any of its responsible officers may recommend a decision or
(b) any such procedure may be omitted in any case in which the Administration finds upon the record that due and timely execution of its functions in the public interest imperatively and unavoidably so requires.