What source do you want? The app literally asks for your phone number, name, profession. Which of these details make you think "anonymous" has any meaning at all.
If a person is found COVID positive, all the traced contacts will be under high-risk. In that case the details are sent to the cloud/governments to take apt precautions and to quarantine the individuals.
Even Apple/Google's contact tracing app send your personal data to the cloud and "works closely" with governments.
Source: https://www.apple.com/in/newsroom/2020/04/apple-and-google-p...