There are plenty of exceptions police can get to bypass warrant requirements. Think for example of stingers and other cell spoofing systems or the license plate readers they have on the front of their cruisers. Even if they do have to get a warrant judges are far more likely to simply grant any warrant request if it has to do with digital surveillance. Carpenter v. United States and Chatrie v. United States have outlined this behaviour, and in the wake of their rulings created the bias towards what are basically automatically approved warrants for such data.