From what I've read on Google's version of the contact tracing support, it is going to be done via Google Play Services and not a security patch or OS update. Which means that it will be pushed via an update from the Play Store.
Apple on the other hand is going to push it via an OS update.
If this is true, then this will only affect those users who use Google Play Services on their devices. If you disable Google Play Services, then there shouldn't be any changes to your device.
In any case, the standard Wi-Fi and Bluetooth considerations against tracking apply - keep them off unless actively using them.
https://static.googleusercontent.com...ion-v1.3.2.pdf