[jlokier]

Yes, those protocols would be available to any cell phone in the world and old devices to the same extent as any other legally-mandated protocol would be.

For example, if government can order than Nokia release a privacy-harming contract-tracing feature, then the government can instead order that Nokia release a privacy-enhanced version based on the Google-Apple protocols instead (or any other better protocols people have developed).

It would be more effective for the pandemic too, because you want maximum interoperability.

And it would be more effective for the pandemic because you will get better compliance too. If people know they are 100% tracked with full transparency they are more motivated to find ways to cheat, especially when doing something "disapproved" (like seeing your secret lover), which is not good for countering the pandemic. People will definitely find ways to cheat the tracing if they are motivated.