This is interesting because it means that they identify themselves as a business.
This is the definition of Organization under the Privacy Act 1988 (Aust)
<<PRIVACY ACT 1988 - SECT 6C Organisations
What is an organisation ?
(1) In this Act:
"organisation " means:
(a) an individual; or
(b) a body corporate; or
(c) a partnership; or
(d) any other unincorporated association; or
(e) a trust;
that is not a small business operator, a registered political party, an agency, a State or Territory authority or a prescribed instrumentality of a State or Territory.>>
This is basically stating that you are not considered to be an organization under the Act if you are a small business operator. This is the definition of a small business operator under the same Act
<<PRIVACY ACT 1988 - SECT 6D Small business and small business operators
What is a small business ?
(1) A business is a small business at a time (the test time ) in a financial year (the current year ) if its annual turnover for the previous financial year is $3,000,000 or less.
Test for new business
(2) However, if there was no time in the previous financial year when the business was carried on, the business is a small business at the test time only if its annual turnover for the current year is $3,000,000 or less.
What is a small business operator ?
(3) A small business operator is an individual, body corporate, partnership, unincorporated association or trust that:
(a) carries on one or more small businesses; and
(b) does not carry on a business that is not a small business. >>
Notice that at Paragraph 1 it states that it can only be a small business if it is a BUSINESS in the first instance (and if it's turnover is $3 million or less). That is, it must be a business to begin with before even considering whether it is a small business or not. Therefore the WTBTS Australian Branch are clearly identifying themselves as a business in the letters referred to on this thread.
There is no definition in the act to identify what a Business is therefore it would revert to the common law definition. They might argue that they are only a business in relation to the Privacy Act but they can't because they have to identify as a business (under common law) before they can identify themselves as a small business under the Act.