15AExtension of time limits
(1)Where a request in accordance with section 12 is made or transferred to a department or Minister of the Crown or organisation, the chief executive of that department or an officer or employee of that department authorised by that chief executive or that Minister of the Crown or that organisation may extend the time limit set out in section 14 or section 15(1) in respect of the request if—
(a)the request is for a large quantity of official information or necessitates a search through a large quantity of information and meeting the original time limit would unreasonably interfere with the operations of the department or the Minister of the Crown or the organisation; or
(b)consultations necessary to make a decision on the request are such that a proper response to the request cannot reasonably be made within the original time limit.
(2)Any extension under subsection (1) shall be for a reasonable period of time having regard to the circumstances.
(3)The extension shall be effected by giving or posting notice of the extension to the person who made the request within 20 working days after the day on which the request is received.
(4)The notice effecting the extension shall—
(a)specify the period of the extension; and
(b)give the reasons for the extension; and
(c)state that the person who made the request for the official information has the right, under section 28(3), to make a complaint to an Ombudsman about the extension; and
(d)contain such other information as is necessary.
Section 15A: inserted, on 1 April 1987, by section 9(1) of the Official Information Amendment Act 1987 (1987 No 8).
Section 15A(1): amended, on 1 April 1988, pursuant to section 90(d) of the State Sector Act 1988 (1988 No 20).

Many of the details I expected to see were witheld by MBIE under Section 9 of the OIA Act. Here is that part of the law:

9 Other reasons for withholding official information
(1)Where this section applies, good reason for withholding official information exists, for the purpose of section 5, unless, in the circumstances of the particular case, the withholding of that information is outweighed by other considerations which render it desirable, in the public interest, to make that information available.
(2)Subject to sections 6, 7, 10, and 18, this section applies if, and only if, the withholding of the information is necessary to—
(a)protect the privacy of natural persons, including that of deceased natural persons; or
(b)protect information where the making available of the information—
(i)would disclose a trade secret; or
(ii)would be likely unreasonably to prejudice the commercial position of the person who supplied or who is the subject of the information; or
(ba)protect information which is subject to an obligation of confidence or which any person has been or could be compelled to provide under the authority of any enactment, where the making available of the information—
(i)would be likely to prejudice the supply of similar information, or information from the same source, and it is in the public interest that such information should continue to be supplied; or
(ii)would be likely otherwise to damage the public interest; or
(c)avoid prejudice to measures protecting the health or safety of members of the public; or
(d)avoid prejudice to the substantial economic interests of New Zealand; or
(e)avoid prejudice to measures that prevent or mitigate material loss to members of the public; or
(f)maintain the constitutional conventions for the time being which protect—
(i)the confidentiality of communications by or with the Sovereign or her representative:
(ii)collective and individual ministerial responsibility:
(iii)the political neutrality of officials:
(iv)the confidentiality of advice tendered by Ministers of the Crown and officials; or
(g)maintain the effective conduct of public affairs through—
(i)the free and frank expression of opinions by or between or to Ministers of the Crown or members of an organisation or officers and employees of any department or organisation in the course of their duty; or
(ii)the protection of such Ministers, members of organisations, officers, and employees from improper pressure or harassment; or
(h)maintain legal professional privilege; or
(i)enable a Minister of the Crown or any department or organisation holding the information to carry out, without prejudice or disadvantage, commercial activities; or
(j)enable a Minister of the Crown or any department or organisation holding the information to carry on, without prejudice or disadvantage, negotiations (including commercial and industrial negotiations); or
(k)prevent the disclosure or use of official information for improper gain or improper advantage.
Section 9(2): amended, on 1 April 1987, by section 4(2) of the Official Information Amendment Act 1987 (1987 No 8).
Section 9(2)(b): replaced, on 1 April 1987, by section 5(1) of the Official Information Amendment Act 1987 (1987 No 8).
Section 9(2)(ba): inserted, on 1 April 1987, by section 5(1) of the Official Information Amendment Act 1987 (1987 No 8).
Section 9(2)(g)(i): amended, on 1 April 1987, by section 5(2) of the Official Information Amendment Act 1987 (1987 No 8).
Section 9(2)(g)(ii): amended, on 1 April 1987, by section 5(3) of the Official Information Amendment Act 1987 (1987 No 8).
Section 9(2)(i): replaced, on 1 April 1987, by section 5(4) of the Official Information Amendment Act 1987 (1987 No 8).
Section 9(2)(j): replaced, on 1 April 1987, by section 5(4) of the Official Information Amendment Act 1987 (1987 No 8).