From a brief look at the article it appears that this works by your phone asking the device purportedly belonging to the caller if they did in fact make the call. So it's authentication at the device level, not at the network level.
Unfortunately it only works when both the recipient of the call and the purported originator of the call both have properly configured Android phones. It would be nice if Google could have implemented this in such a way that it would work with a combination of both Android and iPhone devices, and didn't rely on a handful of Google-specific apps. If they could have done that it would likely have worked on well over 90% of mobile-to-mobile calls with little to no setup.
