It probably means that an "outside agency" was assisted or that they assisted an outside agency - which could just mean another law enforcement division such as a police department in another jurisdiction. For example, a police officer stops you in your local county. Another county has a warrant for arrest which comes up when he requests a statewide search on your name and driver's license. You are arrested and brought to jail and held so that the police department from the other county can pick you up and transport you to their jail for holding, charges and potential prosecution of your case. In this instance, the local police department assisted an "outside agency" which is nothing more than the police department in another jurisdiction.