The following link compares life cycle emissions for the use of natural gas and coal in the US:
In particular look at fig 4 and 8. Fig 4 suggests that, for the LNG cycle, at least 0.3 tonnes of emissions will come from non emission sources per tonne combustion emissions with about half this coming from LNG production, tanker transport and regasification.
While these figures are all about US alternatives, they clearly emphasize the importance of challenging the gas industry to publish site specific data. Also suggests that there is lots to be said for locating generators close to the gas source.
Would be interesting to compare life cycle emissions from Australian LNG and coal used in Chinese power stations.