our 8 flat complex in Melbourne has just gone through a similar situation. In our case we wanted new letterboxes as the old letterboxes were inbuilt to a leaking retaining wall.
When part of the garden was cleared – a leak was discovered on the rusted steel pipe. The plumber advised that we needed to replace the pipe which extended under cement in front of the car park ($9000) However we found the nearest fire hydrant and it seemed it met the regulations of hose length from hydrant to all apartments.
This did cost $9000 but it did mean that we did not have to tear up the cement.
it also I meant a lot of ringing around all the responsible bodies to try and understand what were the regulations etc. If i as an owner and on the committee had to be paid for the hours I spent it would have cost a lot more!