Paddy Wagon can be deployed in some situations - and it presumably helps chances of success to given event.
Usually it is possible to use it in events that include large crowd of people.
Game states that it helps to control crowd of suspects, but if not available then a skilled officer can succeed without it.
It is not available in the beginning, you can obtain it during game:
- earlier, there is a request (unofficial/illegal) for your policeman to help some people and in exchange you will be gifted the Wagon
- later on you can just receive it from the city (e.g. on 24th day)