The don't need it for the world, just rich industrialised cities, this makes the amount of data much lower. Also, I'd guess "publicly available" doesn't mean public domain, but available for purchase by the public or (and its common in developed cities) generated by the government (for flooding, mapping uses etc)
Furthermore, the article does not mention a 3d model of the world from Lidar data either - it specifically mentions just San Francisco
It's also easy for them to make a very specific, narrow list of locations where the data is needed.
Just look at the raw GPS measurements and look for signs of trouble (high uncertainty, coordinates "teleporting" users around unnaturally, etc.). Maybe you only need it on certain particular streets within a city.
There are commercial LIDAR drone services you can hire, so worst case they just pay some of those people to give them 3D models for the specific areas where they have the worst problems and the highest traffic, and they get a huge improvement.
Furthermore, the article does not mention a 3d model of the world from Lidar data either - it specifically mentions just San Francisco