Bluetooth penetrates walls, and travels some distance in all directions, so it will also record a lot of false transmission events, for example in blocks of units, offices, and on public transport. Most transmissions are to immediate family, who are easy to trace manually with the existing procedure.
The government says that if you are party to a (genuine or false) transmission event, you will be contacted by phone, but you will not be told the name of the person who tested positive to the virus. So how will you know if the event is genuine or not? It could be your neighbour on the other side of a common wall, or a colleague who works in the office next to yours -- in either case, no transmission. Also, they say you may be "advised to self-isolate". This is disingenuous -- you are more likely to be ordered to self-isolate under penalty of fines or gaol time. No mention of that in the glossy "Utopia" style promotional video, just happy young models having coffee.
