New Zealand seems on course to mandate tobacco plain packaging legislation; we'll see how the Australian court challenge pans out.
There isn't any real-world evidence on the effects of cigarette plain packaging legislation, mostly because nobody's really done it yet. What we have are a bunch of surveys of smokers and non-smokers on how cigarette packaging makes them feel, whether they think different designs are more or less likely to encourage them to smoke, and the like. In other words, a bunch of hypothetical musings in low consequence environments.
If we're stuck having Tariana Turia's proposed legislation, let's do some good with it. Set it up as an experiment. Implement plain packaging in part of the country, but not elsewhere. Then see what happens. If it seems successful after a few years, implement it everywhere; if it doesn't, abandon it. Either way, publish all the results so we have a better handle on what works. So plain packaging in Christchurch but not in Dunedin, in Wellington but not in Rotorua. I'm sure there are plenty of folks who specialize in designing randomised control trials of this sort who'd be able to run things. We may need a third treatment group to avoid problems that can result when you know you're part of a treatment group as compared to the control, but other folks know more about these design issues than I do. We'd probably also need to compensate the tobacco companies for increased distribution costs over the duration of the trial - the excess of current tobacco excise revenues over demonstrable costs to the health system should provide plenty of money that could be used here.
If we apply plain packaging to the whole country at once, we have no way of knowing whether the policy does anything. A careful randomised control trial could tell us something useful.
I've reasonable "get off my lawn" opposition to the policy, but if we're going to be stuck with it, why not learn something at the same time?