Legal Question in Traffic Law in Massachusetts

There are two ways that a police officer can lawfully stop a person in a town other than the one in which they are employed. For some crimes the police have the authority to cross town lines when in pursuit of a person. The second way that the police may lawfully stop a person in another town is that the police may be employed in one town but be a "special police officer" in other towns. The towns frequently do this because they want the police to be able to exercise police powers when in the adjoining towns.