I briefly scanned the pdf report linked by the new york times, and it seems that one of the ftc's ideas is to basically make the private browsing option available in more browsers, a bigger, bolder and more obvious button, and also probably the default option.

So, I think if they were to follow through with this plan, they probably wouldn't deal with lists or anything, but would have each browser send a blip to the website saying the user is opted in.

The only idea that comes to mind is auditing advertising companies, but it doesn't seem too likely/feasible to me.

well, if the default is not to be tracked, then you never assign a cookie to anyone unless they opt-in