Hi Sea Bee, you may have resolved this issue as I note that it has been some time since you posted and no one has replied.
Briefly…
These people are acting like cowboys. I cannot see that this somewhat strange procedure in any way complies with the SSMA. Under Section 110 an ordinary resolution is required for Minor Renovations. Any work that involves the common property requires a Special Resolution or a special by-law. This must be done prior to the work commencing. You can always apply to NCAT for a stop work order. If the issues are serious and may compromise the common property you might want to talk to a Strata Lawyer.