In January of 2008 the City of Kent Police Department became one of the first agencies in Washington to begin using automated camera technology on their patrol cars to scan license plates.  The three camera system is mounted on patrol cars and in its first six weeks, scanned 100,000 license plates and located 25 stolen cars.  The system was integrated with police databases for stolen vehicles, so that every time a police car is driven, it automatically is scanning license plates.  What used to require a police officer to either radio in, or at least type into the computer was now done automatically. http://www.seattletimes.com/seattle-news/camera-system-scans-for-stolen-cars/

The City of Tacoma also added the device in 2009, and by June of 2014 had them in three of their to their patrol vehicles.  By this time the technology had improved to allow the devices to be linked to databases that could also show amber alerts, and those with warrants.  Additionally, officers who drive cars with the cameras are able to turn them on and record every license plate they encounter, and often would drive them to the area that a shooting was reported in order to provide that information to detectives who investigate the shooting, later one. http://www.thenewstribune.com/news/local/article25870453.html

The ACLU has spent a considerable amount of time and effort investigating the use of this technology in Washington, and in 2011 they found that:

The first thing we discovered is that law enforcement use of ALPR in Washington has become relatively common and widespread. At least 22 city police departments and county sheriff's offices across the state reported owning ALPR systems, and we assume those numbers have only increased since 2011. The majority of those agencies had placed their systems on vehicles rather than fixed poles.

We also learned that ALPR systems have the capability to record and maintain an extraordinary amount of data about individuals. In Seattle, for example, police department ALPR units accumulated 7.3 million license plate and location records to the department's database during a three-year pilot project. Of those 7.3 million records, a scant 7,244 came up as hits, for a scan-to-hit ratio of less than one tenth of one percent. Or put another way, the Seattle Police Department photographed vehicles and recorded the exact time and location of the photo for individuals who were merely driving around in 7,369,416 instances. https://aclu-wa.org/blog/automated-license-plate-recognition-newest-threat-your-privacy-when-you-travel & https://aclu-wa.org/blog/alpr-surveillance-tool-you-ve-probably-never-heard

Since the time that Automatic License Plate Recognition Systems have been installed in Kent, I have seen them used for purposes other than just scanning of license plates.  I had one case where an officer who was looking for a hit and run driver, and who already had their license plate and registration information, used the "search" feature of the Automatic License Plate Recognition System to look at historical data and photos, where he determined that the car in question had been parked in the employee parking lot of a local business. Using this information, he went to human resources at the business, and was able to determine that the registered owner was an employee at this business and he proceeded to question her there.  

I don't think it is farfetched to assume that Automatic License Plate Recognition Systems will soon be standard equipment on every police car in Washington, given their ability to automate tasks that police officers perform much less efficiently.