See http://www.unisa.edu.au/Fin/Tax/gst/faqsGST.asp#Do all businesses charge
Receiving Quotes and the GST
The general rule is that where a quote is supplied with no mention of the GST, it is reasonable to expect that the price is GST inclusive. This is the view supported by law.
THE TRADE PRACTICES ACT 1974 AND UNLAWFUL PRICING
The TPA requires that:
Consumers are not misled or deceived about the total price that must be paid to receive the goods, services or packages advertised.
When a price representation is made, the total quantifiable price is clear to the consumer.
Advertising, displaying or listing separate components of price without also giving the total price payable may constitute a breach of the TPA if presenting the price in such a way is ambiguous or the total price cannot be readily calculated.
Thus if you received a quotation with no mention of GST and you would normally expect to pay GST it seems reasonable to expect that GST is included in the price. Otherwise the quotation would fail the above.