Not sure if there is a way around it. The way I understand it works only if you are already a Optus Mobile Postpaid - My Plan Plus (Data Sharing plans) customer.
No end date specified in the Web Site. I just marked it as 30th April.
This is cheaper than the Apple store prices. Though you are buying it on contract, apparently the device is not SIM Locked (Haven't tested this, but what I heard from the Store guy).
IPAD Mini 2 16GB LTE - $365 ($15 * 24 months + $5 once of Data Sharing SIM)
IPAD Mini 2 32GB LTE - $485 ($20 * 24 months + $5 once of Data Sharing SIM)
IPAD Mini 2 64GB LTE - $533 ($22 * 24 months + $5 once of Data Sharing SIM)
IPAD Mini 2 128GB LTE - $593 ($27 * 24 months + $5 once of Data Sharing SIM)
You can get the same price if you pick month to month as a new optus customer