I am one of the folks who has been advocating this (Class E down to the instrument approach minima, not 1500 feet) for years, but MJGAHAN is correct when he alludes to the fact that controlling IFR aircraft in Class E is very inefficient without surveillance. One of Australia's problems, however, is that the service providor, Airservices, is actually a money-making venture for the Commonwealth Government. Hence surveillance has never been used where there is a need, only where money can be made. This can be proven by looking at the RAAF roll-out of surveillance at bases that do not support anywhere near CASA/Airservices criteria for installing surveillance. (Whatever that is, I can't find it anywhere). This money-making venture is also the reason why Australia has capital-city priorities and that well-worn phrase "Clearance not available". A service providers job is to provide a clearance not tell pilots why they cannot have one. OK, tirade 1 over!
The situation in Australia now is that if space based ADS-B surveillance is used (and it is available) then the position of every cooperative IFR aircraft in the two FIRs is known to ATC and can be displayed on a sutably set-up surveillance display. This means that the Class G traffic service so beloved of ex-FSO Griffith, and proven not to work when it was really needed at Mangalore, can now be replaced with a separation service utilising Class E airspace. Over the years I, and others have implored CASA and the ATSB to introduce/recommend this airspace but unfortunately they are both arms of the same Department that benefits from the income provided by Airservices, so the three monkey trick is always pulled out. See no evil (we do not believe there is an issue) hear no evil (What is wrong with traffic information) and speak no evil (anyone sticking their head up and speaking out of line will be shot on sight). OK tirade 2 over!
Now their are no more excuses - the ATSB will produce a report on the Mangalore crash, hopefully sooner rather than later, in which, if they do not say that a Class E control service could have saved four lives, they will have disregarded their brief. ICAO Doc 9765 Manual of Accident and Incident Investigation Para 1.1.2 (my underlining)
"An aircraft accident or incident provides evidence of hazards or deficiencies within the aviation system. A well-conducted investigation should identify all immediate and underlying systemic causes and/or contributing factors of the accident or incident. The investigation may also reveal other hazards or deficiencies within the aviation system not directly connected with the causes of the accident. The emphasis of an aircraft accident or incident investigation shall be on determining why the accident or incident happened and on recommending appropriate safety actions aimed at avoiding the hazards or eliminating the deficiencies. A properly conducted accident investigation is an important method of accident prevention."
So - if I was Airservices i would be making sure that when/if a "well-conducted invetigation" is produced they are in a position to pretend that they were ready to go before the Minister gets embarrassed.