Agree rastus, if the government remains in gridlock over the CET, it will only ensure higher wholesale prices through 2018. Interestingly, looking at the graphs below from RenewEconomy, highest wholesale electricity prices for Queensland coincide nicely with the start of operation for Kidston 1.
However, declining wholesale electricity prices isn't too much of a concern considering we have a 20 year PPA with the QLD government, which is likely to be somewhere between $80-100MW/h.
Depending on where the 'clean energy' threshold was set for a potential CET however, GNX would certainly benefit from selling credits to polluting power stations, providing another source of revenue. This could give extra incentive to expand the Kidston Hub in the future, but won't necessarily impact on current projects.
The CET is more for providing investor certainty for "clean" projects, but again that depends on where the threshold is set. It is likely that to get a majority in the coalition party room supporting a CET, the threshold will be set so as to allow some "clean coal" and gas to benefit, which makes the whole thing pretty useless. So in the end, it's implementation probably won't have much material impact on GNX either way.