Seems that new international students coming into MEL airport, get a cabcharge one use vouchers, using qr code, for incoming students, as on Reddit, scary that they will fall prey to the tricks of the taxi drivers.
Poor new students, open to the tricks of the taxi drivers, as are new comers.
Also, now that they have moved the taxi rank to where the valet used to be, its now not a straight one, for the T1/T2 side... I think from my quick look, its a row of 5 and about 10 cars can go in and out per row, so quite compact, and the taxi drivers wouldnt like that.
Meaning they would in time, put more emphasis on the touts onto that plaza, probably at the times they feel its most worthwhile.
Out the front, it seems that uber has taken front of shop, ranking.