At the very least, counting the emissions from coal produced in Australia on Australia's carbon emissions ledger and attaching the 'externalities' to the producer makes more sense.
If you cannot ensure a consumer is affected, it won't change consumption (which is what we want).
It's also just easier to do the accounting on the producer-exporter side.
So far the nations of the world have not shown such a unified stance.
Most realistic and effective solution will be to get the biggest producers and consumers to all agree to join the system, whilst at the same time agreeing to place tarrifs on trade with those that won't join.