New operas are like hens' teeth in Australia. As government subventions steadily diminished, so adventurism – especially at the national Opera Australia – declined. So two adventures by OA in 2015 need to be hailed, both for their novelty and for the role they have played in increasing the audience for opera.

First there was the television opera The Divorce by Elena Kats-Chernin played over four nights on the ABC like a soap opera. Then there is The Rabbits, a festival tourist since last February, finally to be seen at the Sydney Festival, initiated by the OA's Artistic Director Lyndon Terracini, but composed by and starring the cross-over queen, Kate Miller Heidke. She was classically trained in Queensland but has had four platinum popular discs to her name as well as singing at The Met in The Death of Klinghoffer and at ENO. Terracini – a significant baritone tackling mostly contemporary work in his day – has been criticised for a company policy increasingly dependent on Verdi, the glamorous Handa Opera on the Harbour and an annual musical. 2015 has shown him quietly doing his best to position opera where audiences may be surprised to find it.

For The Rabbits began life in 1998 as a children's book written by John Marsden – a man with 3 million sales under his belt – and illustrated by Shaun Tan, who's gone on to write his own successful books and works in both theatre and film as a designer. The book's been reprinted 35 times – extraordinary for something that is the simplest of allegories about the colonisation of Australia (or anywhere where there were Indigenous people) – Rabbits in their millions being the Brits, and a decreasing number of Marsupials being the beleaguered natives.

Do audiences for the opera therefore respond as enthusiastically as they undoubtedly did to this political allegory? Or to the serious emotions around the Marsupials' Stolen Children? To the mixed musicality of rum-te-tum opera for the Rabbits, Lloyd-Webberish matter for the all-Aboriginal Marsupials, and her own unique colaratura for Miller-Heidke as the narrator Bird? Or could it be that it's the visuals initiated by Shaun Tan and amplified by stage designer Gabriela Tylasova that offer constant delight to the eye and interpretive assistance to an audience including children eight and up?

Undoubtedly Tan started this predominance. His bleak and increasingly industrial settings and his creation of cuddly numbat Marsupials and self-important fat-bellied colonial Rabbits come straight from book to stage. Tylasova, however, has add a Constructivist helter-skelter to centre the action. And director John Sheedy has added emotional touches like ribbons falling from an empty sky after Marsupial joeys have been carried out of sight on kites over the keening of their mothers forcefully rejecting the assimilationist assurance, “One day your children will become Rabbits too”.

Differences between the two tribes have been established early. While an over-long sequence has the Marsupials telling a Dreamtime story about lizards, ending “The land lives and the lizard learnt to fly”, the first Rabbit arrives in the person of a caricature Scientist (Kanen Breen) pushed in a Heath Robinson cart by A Convict (Christopher Hiller), and the self-same lizard is seized and stuffed into a specimen jar. It was a pity Marsupial David Leha didn't spear the Scientist then and there before a whole mob of wingeing Poms arrived by boat and began the take-over in the name of Empire!

Despite some ineffective spearing, the stage is soon festooned by smoking chimneys, fluttering flags and flown-in tower blocks – alcohol for the natives, tea for the gentry. In charge, Robert Mitchell as The Captain particularly enjoys his egotistical escape from the OA Chorus where he's tackled 110 operas! Jessica Hitchcock is his Marsupial match – hitting soul heights and leaving powerful memories at the end as both tribes face up to a barren present with her anthemic “The land is bare and brown and the wind blows empty across the plains” – leaving just herself and the Convict to try and conjure a future.

Kate Miller-Heidke, on the other hand, created problems for herself. Her Bird's score is so musically intense that her important role as Narrator often left the clarity of her words behind her music. But the show's message certainly got through entertainingly time and time again. Whether it will work for Maoris in New Zealand, Bantu in South Africa or First Nations in North America is less certain. Even I was left slightly uncertain as to whether the lively five-member band's finale in Klezmer mode was intended to suggest that post-War migration from southern Europe and the Eastern Mediterranean was any sort of political solution, or just a way to milk the applause!