The reason they never made it
I've never heard of Anvil till I heard about this movie. I finally saw it and I know why Anvil didn't make it. Their songs suck. Robb is a kick ass drummer, but the songs have horrible lyrics and aren't aren't good at all. Metal on Metal is laughable and sounds like a 3rd grader wrote it.
And I don't know if the one scene was staged, but it was straight out of Spinal Tap. When they are eating at some burger place (just like Spinal Tap) they talk about their song Thumb Hang and sing a little of it. It's right out of Spinal Tap when they sing All the Way Home.