Certainly at the independent level in a given city. Everyone plays shows at the same bars and clubs. Most of the audio engineers are either in bands or were in bands and then got into producing. Our situation was a bit different, the guy who mixed our second CD for us was actually pretty successful in the Toronto scene. He normally wouldn't have worked with us but did it as a favour because my ex wife (she was my gf at that time) had interned at his studio as part of her degree in radio and television arts. So she did most of the audio engineering on the CD but he did the final mix because she didn't really have the skill set to do that. Met some cool people through him. I don't know if you know the band Big Wreck, they were pretty big in Canada but I got to meet them through that same producer.