Australia, geographically isolated from much of the rest of the world's ecosystems, prides itself on its extremely stringent quarantine regime, as anybody who has ever taken anything made of wood or straw through an Australian airport will know, so the idea of introducing any new species (especially elephants) is bound to be controversial, to say the least. Professor David Bowman (the proponent of the scheme, not the astronaut in 2001) says that the elephants and rhinos wouldn't be allowed to roam freely and reproduce, but would serve as a carefully monitored "machine" for pruning the grass, with each being tracked with a GPS transmitter and otherwise meticulously accounted for. Other scientists, however, are sceptical about whether elephants are necessary or whether introducing them, even in a tightly controlled fashion, wouldn't lead to more unintended consequences.
Oh dear. Professor Bowman is my boss / head of my lab. His office is across the hall from mine, and his phone's been ringing non-stop since yesterday. He's nicked off to Arnhem Land, however ;)
Pretty much the same thing happened with Kudzu grass/vine in the US south. Seemed like a good idea at the time (cows ate it, kept soil erosion at bay, grew quickly and easily in desert environments). Then it got out of control. See cover of R.E.M.'s Murmur.
I like the idea of elephants in the Australian desert. They can keep the feral camels company.