If there really was patent infringement, then it would be difficult to erase all traces. Similar to the Zenimax Oculus lawsuit where computers were erased, but the verdict still came down against Oculus.
Civil case. Preponderance of evidence is enough. And the defense standing over a shredder pushing stolen documents through, paying for the shredding of a hard drive in cash months after it was supposed to be done, delaying discovery and magically disappearing a boatload of files from a company already known publicly to act scummy looks a fucking lot like a preponderance of evidence. All Waymo needs to do is tell the story the way they see it to a jury - too many dots connect up perfectly.
My guess is that the only reason this case is still going is that Uber can't come up with settlement terms (i.e. billions of dollars of cash) Waymo will accept.
If I invent something and Patent it, you can independently invent it and you're still infringing on my Patent.
Provenance is only important for Copyright and Trade Secrets.
(I think. IANAL.)
There are bad taxi laws out there, but the number of good taxi laws is not negligible.