When they rego check ie. pink slip they are only checking for obvious problems like brakes and tyre wear not what material your bonnet is made out of.
Someone might confirm this but if you look around hard enough I think there are a couple carbon fibre bonnets that are ADR'd which might involve them being laminated so when an object hits them they don't fragment into little ninja stars but then again those people might have been bullshitting when stating that they exist.