In the same way that George Martin used his experience and expertise in the studio with the The Beatles, Martin Hannett used his studio craftsmanship to shape the sound of Joy Division. As the article states, without his (and others) input they may not have been what they were. Having listened to their albums (an actual perfect discography), their demos, outtakes and other rarities, I think this definitely rings true. My first exposure to their history was the film 24 Hour Party People, which I think actually does justice to them and the scene that they were a part of.