[crushthecurve]

In a regional context a bluetooth proximity app offers even less theoretical value.

A contact is only registered after 15 minutes of time spent within an estimated proximity of 1.5 metres (itself a primitive model of infectious disease transmission based on a 1942 paper). Note other countries set the distance at 2 metres.

As outlined in other comments in this thread, close contact rules include anyone in a room for more than 2 hours, so even though all close contacts have to be manually interviewed (there is no instantaneous notification and isolation) for most social situations close contacts won't be registered through crude estimates of proximity: home, family / friends, work all require thinking about and providing contacts.

When you strip out all the situations that aren't beneficial, that starts to leave public transport in major metro situations where commutes are greater than 15 minutes.

Keep in mind that also implies the end of any social distancing (as otherwise no contacts are registered). That seems obvious, as public transport becomes overwhelmed if capacity is significantly reduced.