That's interesting... and a bit like what some so called...

That's interesting... and a bit like what some so called "bootlegg " retailers did back in the state tobacco tax days ( buy wholesale smokes in Qld @ lower state tax rate and then ship to NSW or VIC who had higher tax rates...some individuals made a fortune before the loophole was closed via the Commonwealth taking over the scheme.)
Anyway .. your concept would properly work in principle ( less the transport and transaction costs) however the risk / reward ratio would be huge when ( not if) caught.. Think the industry is under enough pressure and scrutiny already and any attempt to subvert this erroneous evil tax would just bring further greenie wrath and public condemnation.
My guess is they will just suck it up as long as it is QLD. only . The ones who will have to suck the most are the Metallurgical Coal producers who command a higher price per tonne as the tax does not differentiate between Thermal and Met. coal ...just another example of gross over reaction and incompetence by the State Gov.