Multi-quoting is a bitch on the iPad so bear with me.
Firstly, the Australian government is still the issuer of debt. Unless, it is an actual LNP policy, securitization of hecs debt, in of itself doesn't mean it will stop being interest free.
Secondly, the nature of hecs debt is that it is indexed to inflation so the real value never changes. By securitizing the loan, it's effectively making it a really shitty CPI bond. The value that comes from investing in this comes from the discounted NPV. So for example, I've heard that some bankers would only be paying $6-8b for the $23b debt. On that note, any risk that arise from recovery or whatever would most likely be factored into price anyway
Finally, it's by definition impossible for a GFC to occur on hecs debt because default can never happen. The principal is repaid according to a percentage of income >$51k. Below that you don't pay anything.
The government is basically liquidating some of its assets so it's not a doomsday tactic most think. The polo popo did raise a good point that collection through the ATO would make it weird as fuck. Also considering the fickleness of payments, due to it being a proportion of income, raises the issue of how debt securities is marketed and what obligation, if any, does the ATO have in disseminating payment information of students. It's nothing like the American system