"Cross-sectional survey during the roll-out phase of the law, analysed by timing of survey."
"How does increasingly plainer cigarette packaging influence adult smokers’ perceptions about brand image?"
The BMJ study, "Introduction effects of the Australian plain packaging policy on adult smokers: a cross-sectional study", found that plain packaging helped increase the urgency for smokers to quit. That's a causal link to reduced smoking levels.
The BMJ study "How does increasingly plainer cigarette packaging influence adult smokers’ perceptions about brand image? An experimental study" found that plain packaging helped reduce brand interest, helping reduce uptake by younger people. Again, a causal link to reducing the rates of smoking.
The surveys do provide plenty of evidence that plain packaging changes smoking behaviour. The price of cigarettes in Australia has risen due to taxation . A packet of cigarettes cost $16 in 2013, in 2014 it is now $20.
Edit: I was needlessly aggressive. Sorry.