A summary of the issues is here, along with many answers to your questions:
https://www.lpi.nsw.gov.au/__data/assets/pdf_file/0011/25949/Access_to_neighbouring_land.pdf
Can I suggest that, in addition to your other requirements, that your OC creates a clause whereby a penalty must be paid by the developer to your OC for every day that the scaffolding remains on your common property after the 6 month limit? I am sure that the developer has these types of clauses with his subbies!
Such an agreement may need approval by the OC because your OC is entering into a contract for the use of the OC common property. In which case the neighbouring developer should also pay for the cost of the OC meeting.