"Rubbish?" I do not understand. I believe they smiled because they were doing something they were good at... Causing chaos. *smiles* Lovely.
Do you mean: "How could they think it is rubbish?? It's a BMW!" They think it's rubbish because they know it isn't real and it doesn't matter to them. They need only to reach their goal: to retrieve the Keymaker, in which they fail horribly. Tsk tsk.