[cptskippy]

Why on Earth do you think backdoors and ML having any part in the solution?

Telcos peer with one another and trust each other's traffic implicitly, all they need to do is stop trusting implicitly and ask for verification for things like caller id.

A Telco may not know where a call originates but they know what Telco it's coming from and can pass responsibility for fines back to that Telco.

Since no Telco wants to be saddled with fines, they'll quickly pass it off and it will eventually reveal the origination.