The plan is open term so you can cancel at any time and still keep the $400 discount. You will need to sign up in store: 2D, JB, Noel Leeming, Harvey Norman, PBTech all have this deal.
If you pre-order (11 April is the last day) you get a bonus Huawei GT Smart Watch (via redemption).
If you pre-order from Noel Leeming you get bonus JBL Everest 710 Headphones as well.
If you pre-order from PBTech you get a bonus UE Boom 3 speaker + power bank as well.
This has been discussed in various forums and sounded too good to be true but I just got written confirmation from 2 Degrees today:
"In regards to Huawei P30, there is $400 off the RRP, which means that the remaining amount on the RRP gets spread over the term you choose.
If you wish to cancel the plan , you just pay the remaining on the phone. So, RRP is $1099 with $400 that comes out to $699 which will get spread over the term."