The privacy rules have been defined, see the legislation link here…
The issue appears that the States are responsible for managing notifications when there is a confirmed contact…and yet to set up the systems to do this. It should be relatively straight forward to do…and if one waits for this to be sorted contacts between now and later installing the app will be missed (up to 21 days). There could have been close contact with someone with COVID-19 in this time, and one would not know if contact tracing was not occurring. This poses a risk, particularly if one is in a high group or comes in contact with high risk individuals (such as elderly family or community members)
