Assuming a buyer in either in Latin America or Southern Africa.
There are no heavy lift liner services from Tasmania to either of these destinations, so it will require the charter of a vessel (hopefully one that has had a paying cargo to the mainland).
A small heavy lift vessel with adjustable tween decks will be needed, anything under about 8000 tonnes will probably have insufficient height to double stack locomotives, so work on something similar to BBC Chartering's Bergen Class
In cross section this type will give 3 locos wide x 2 high, with a theoretical max of 18 units.
Cost of charter with wharfage, stevedoring, and insurance, probably in the range of A$1 to A$1.5 million.
So a minimum locomotive buy would have to be at least 10, to justify, and amortise the charter cost, better 12 or 14, to land them at under A$100k per locomotive.
Previous Tasrail locomotive disposal tenders have had a relatively short notice. For a Latino (or African), to obtain an Australian visa (our overseas embassies and consulates can be tardy and not present in all countries), and book flights, you must allow at least 6 weeks, so a gap of between 10 to 12 weeks between the tender been published, and closing is desirable, with flexible inspection times allowed for overseas bidders. Inspection windows for previous disposal tenders have been arbitrary. Tasrail is theoretically a Limited Company, why let the civil service mindset govern disposal tenders?
Previous loco disposal tenders have facilitated local scrap merchants. If Tasrail wanted to maximise returns, they should have a list of potential overseas bidders, and give these people advanced notice, this will increase their return, as the overseas buyer purchasing rebuild core, will pay a premiun over local scrappers. Also arrange the tender process to favor the bulk purchaser, all of the QR class for instance with the option as a job lot, will probably attract a better price than if sold piecemeal as single units.