By the judicial system, obviously. Uber's lawyers will review the warrant and if they agree that it's proper they will instruct their sysadmins to provide ONLY

By the judicial system, obviously. Uber's lawyers will review the warrant and if they agree that it's proper they will instruct their sysadmins to provide ONLY THE DATA COVERED BY THE WARRANT to authorities. If they don't feel the warrant is proper, they will fight it in court. The vast majority of times warrants are upheld, so really all that happens is the authorities are only granted access to the data they had probable cause to request. What you're suggesting is that the authorities should have access to anything and everything that a person who happened to be logged in at the time of the raid had access too. You are suggesting that the authorities should always be granted arbitrary access to a random amount of data, which is almost certainly not relevant to their case, any time they get a warrant for any data at all. Further, you are acting as if that article is the end of the story, but it's not. There will be legal review by relevant professionals and Uber will provide whatever it is legally required to provide.