Just wait until someone installs a listening device somewhere in the cab. Doesn’t need to be Waymo doing the listening. Target Waymos that operate around financially important areas like tech and finance companies and profit.
They do record video though, so you'd have to figure out a way to install it such that you aren't suspected of installing it. Plus how do you get it back? You could put in something with a cell modem, but then how do you power it more. There are USB ports tho, so you could ride in the front seat and make it look like a charging cable or battery that you just forgot, but really it's a listening device with a cell modem. For all that effort, you'd want some serious ROI and youd want to do some math on the chances you get something actionable that isn't going to get you investigated by the SEC anyway, and then further, you can't do it a bunch of times because that's really how you get caught. Nah, better to actually get employed by a company, and the higher up you go, the bigger the crimes you can commit!
Sounds like something out of Billions.
That can be done in any cab. Heck a driver would have a much easier time covertly recording you.