What they may want to consider is a team of people to actually take the calls and trace them back to the source. Or at least the people that are making money in some way. And don't say or react 'oh that wouldn't work'. Of course it would work if done correctly. No point in selling health insurance by way of a third party making calls or on your own if it will get you in hot water.
From what I can tell nobody is making robo calls to simply be annoying. It's quite different than a DOS attack done for fun or many other 'crimes' if you want to call it that.
Not that they shouldn't approach this in the way they are. But to simply make as if there is no way to get the perps is a bit ridiculous. Someone is in the end selling something or collecting some name or something like that.
I am reminded of what I thought back when graffiti was a bigger deal than it is now. Why not simply set honey pots that you know are going to get tagged? Or monitor various locations likely to get graffiti.
Now this doesn't mean that offshore people with scams won't get involved. That could happen. But as a start might make sense to at least gut the people in the US that are benefiting from this (in addition not instead of other 'remedies' by the carriers).