When I purchase potted
plants from commercial suppliers they send a phytosanitary certificate with the plants.
Other commercial suppliers that I have bought stuff from send their plants bare-rooted, and for this it appears that they don't need a certificate. It puzzles me somewhat as there are potential issues other than soil-borne ones, and yet many mainland suppliers routinely send to Tassie as long stuff is bare-rooted. In the past, and even this spring, I've got loads of bare-rooted fruit trees and some herbs from Greenpatch with no problem.
There are exceptions for weed-species of course, and some fruit and vegie species - you can often see mainland catalogues where 'Not to Tas' is plastered across some of the items offered, while the rest are fine. For example, organic tomato, chillie and corn seeds are not allowed. And every Autumn Gardening Australia has a catalogue where there are inevitably some species that I can't get in.
There aren't too many mail-order cacti suppliers though. Of those that I have found some do send potted, with certification, but they are exy! No commercial operation seems to send cuttings, or bare-rooted cacti or succulents.
I'm leary of Ebay; especially as, being a student, I can't afford to bid against the rest of you! (That ant-plant looked fine...). And most Ebay sellers aren't bothered to fuss with certification when it's required.
Sadly, I don't know any Tasmanians with enormous cactus/succulent collections.