Same deal found here: https://www.ozbargain.com.au/node/477586
Went to iiNet website and saw:
ULTRA3 Offer: Get your monthly plan fee credited back for up to 3 months. Offer may be withdrawn at any time. Available in selected buildings. *Typical evening speed indicates download speed and is measured between 7pm-11pm. Actual throughput speeds may vary due to factors such as line length, device and more.
I applied online and got a message saying that the code has been approved, and three months have been added to my order.
Free activation if you choose a 6-month contract, or $99.95 activation fee for no lock-in contract. Both options have a $10 delivery fee for the modem.
Only available to buildings serviced by iiNET/TPG's FTTB network.
Awesome deal, I am on an old Wondercom plan which is $69.99 per month for the same deal. The only way to get the new deal was to leave and rejoin. I can "move" to iiNet, save $10/m and get 3 months free :)
EDIT: Weird, my building is no longer showing as having FTTB on either TPG or iiNet's site.