We bought CPP for our upcoming trip, which was paid in full at time of booking. We are now considering the purchase of the HIA package. HAL will add the CPP premium to that purchase. Note: any single component of HIA can be purchased prior to sailing, without incurring CPP costs and includes the option to cancel within a certain timeframe for a full refund.
To quote the HAL agent: "HIA is considered to be part of the cruise fare".