I see your point, the whole temporary traffic management plan is not enforced.
It could be enforceable if the permanent speed limit was written as 100 in the temporary traffic management plan, so the Gazette is relevent.
The counsel in his respondent submissions has forwarded the relevent Gazette, which can be found here:
http://www.dia.govt.nz/pubforms.nsf/NZGZT/Supplement_Government190Dec09.pdf/$file/Supplement_Government190Dec09.pdf page 4550
It means that from Gillies Ave to Harbour Bridge is 100 kph, but the signage still showing 80 kph. It will be an interesting argument in the High Court