There are 2 different aspects of privacy in Contact Tracing technology. One is regarding device-to-device contact and another is device to cloud. In case of device to device, there's no knowledge if it shares your personal info to other phones.

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...