Right on Gav,

Yes, the 80% solution not the 20% solution! Australia would also become import-independent, surely even Andrew Bolt could get his head around that one.

Alan Kohler did his whole Inside Business program this morning on Emissions Trading. http://www.abc.net.au/insidebusiness/content/2007/s2295654.htm
Kohler seems to have been thrown somewhat by the line on Page 11 of the Garnaut report that it's already "too late" to avoid significant climate change.

Gav,
Note though a lot of browns reductions are for stopping rain-forest destruction and re-planting trees. While Australia has stopped most tree clearing, re-planting is not going to be considered in initial carbon trading. This is probably a serious flaw.
The balance, almost eliminating FF for transportation and electricity production will boil down to replacing FF in transport with electricity and thus generating a LOT more electricity by renewables ( and nuclear?).

I can't see much of the world automobile capacity being used for wind generators because they will be flat out building BEV and PHEV's.
Some steel from not building larger vehicles may be available for wind towers. Surplus aluminium from scrapped aircraft could be used for turbine blades and transmission lines. For Australia to replace 90% of the coal used in coal-fired electricity generation( keeping the coal fired power plants for back-up during days of poor wind, while using hydro to flatten hour by hour changes in wind power) would require us to increase our wind capacity by a similar amount to our entire existing wind capacity every year. With world wide shortages now, we would have to build up a new wind power manufacturing capacity. At least we have surplus copper, steel, aluminium. Similarly for solar PV capacity.

Gav,
Reading Lester Browns article in more detail what he is proposing could be implemented by 2050, but it seems totally unrealistic to replace ALL oil,ALL coal and 75% of NG with wind and solar in 12 years!.
In Australia's situation its clear that we can only make significant reductions in carbon emissions in 12 years by phasing out coal. It seems that the Garnaut Report is taking aim at eliminating coal, with carbon sequestration the sugar an a bitter pill. There is no way that any significant CCS will occur in next 12 years, but could see existing coal fired plants converted to CSM.
Taxes on "other carbon sources" are really included for fairness and increases in petrol prices are going to be collateral damage. The world oil price rises are going to do much more to reduce consumption than any CO2 tax.
Direct legislation to directly reduce coal use(for example mandating 1% NG replacement and 2%wind or solar replacement of coal use per year; much larger capacity changes) and improve vehicle fuel efficiency by 50% could allow CO2 targets to be met with a very mode CO2 tax(much less than required to make CCS viable).
So by 2020 we would have 20% of electricity generated by solar and wind, 6-8% from hydro and a big part of the remaining coal generation capacity able to progressively switch to NG to continue to meet targets beyond 2020. So instead of coal being used as the cheapest base-load, it could be used during longer periods of high demand(heat waves,low wind periods), or low hydro storage(droughts) or as is occurring in WA if there was an interruption of NG supply. Wind and solar would eventually be the low priced fuels, a mix of NG/coal to top-up predictable changes in demand and hydro capacity mainly used for short term grid balancing(greatest value hence highest priced).