The so-called analysis (no copy of which I have yet been able to find) projects that in a double dissolution the Coalition would win seven seats in each of Queensland, NSW and WA, and that in each of these seats Labor would win four and the Greens one.
A double-dissolution quota to win a seat is almost exactly 1/13th of the vote. At the last election the quota split between the Coalition, Labor and the Greens if translated to a double dissolution was NSW 4.44-4.11-1.01, WA at the original election 5.76 (including Nationals WA, which is generous)-3.47-1.23, Queensland 5.38-3.70-0.83. Of course since the Coalition vote was deflated by confusion with the Liberal Democrats, it's probable that it should really be a bit over 5 quotas in that state. But in all cases it's well short of 6.
A party can run as many candidates as it likes but the existence of party voting (which will be recommended on how to vote cards and easier for most voters) will mean that each party with a quota or more will fill as many whole quotas as it has and then be left with a single effective candidate fighting for one of the remaining seats. Thus if the Coalition polls below 6 quotas (46.2%) in a state, all its candidates below the 6th will be cut quickly, removing any chance of winning seven no matter how many eliminated micro-party preferences might flow the Coalition's way.
True, some micro-parties would fold and their voters switch to majors or minors, but this will happen for all parties, not just the Coalition. I suggest that if the Coalition polls the 50% or so in the Senate for these states it would need to win seven, then it will have done so outrageously well nationwide that it would be a huge injustice for it not to control the Senate. After all it got nowhere near that last time in a landslide victory!
Ben Raue in comments at the Tally Room also points out that the analysis is simplistic as well:
"Apart from Antony’s point about the absurdity of the Coalition getting 7 senators in three states, the remarkable confidence with which they predict zero other minor parties from getting elected – with a minimum of six preferences and some parties getting 3-4% and a 7.7% quota it certainly is possible."
The Age article claims it would be harder for the Greens to win two seats in a double dissolution than in consecutive half-Senate elections:
""Under any system of proportional preferential voting the Greens will always find it harder to elect two senators at a double dissolution than to elect one at a normal half Senate election," Mr Askey said.
The Greens generally poll about 0.8 of a senate quota in each state but in a double dissolution their second candidate is left with 0.37 and unlikely to get elected on preferences."
In fact in a bad year the Greens will not normally win that many seats in a half-Senate election (they were lucky to get three, let alone the four they got, in 2013) while in a good year (like 2010) they could well win three in a double dissolution in Tasmania and two in every mainland state bar NSW. Their current standing of ten seats is because they followed a good year with a lucky one, and under the current system they would be likely to be pared back unless the next election was a strong one for them anyway. Removing the reason for micro-parties to compete effectively with them should be more important for the Greens than the murky differences in likely seat numbers won between years under the two systems.
Addendum: See also Antony Green's excellent demolition of this nonsense ( which I had not found when I wrote this one) and especially the comments section in which Askey shows that he, like Breen, has no idea whatsoever by admitting he used two-party preferred votes (ie votes after all preferences are allocated!) to model Senate primary vote shares. An astonishing piece of cluelessness and the Age is obliged to retract the article if it has any interest in keeping the public informed.