This assumption that this ridiculous and inhumane plan will stop people smugglers is reliant on two other fairly big assumptions:
1) That the people smugglers actually care. That they won't lie to refugees that Australia is a valid safe haven. Last I checked, people smugglers weren't the most honest of people. There was an interview with two Sri Lankan men a few months ago that had sold all their belongings for a ticket to Australia because they were told by people smugglers of all the amazing opportunities for them in Australia and that they'd be welcomed with open arms. Of course they were turned back. Returned home where they had nothing left because they had sold everything for a ticket to nowhere.
2) That refugees will actually know that this policy has been put in place and that they will not be granted access to Australia.
Something tells me that these two big assumptions are way off the mark.