Can I use an Australia work visa for tourism?

In general, no, as Department of Immigration and Border Protection notes that entry must be for the purpose that the visa was granted, and a holiday must be with coincident to that entry (added emphasis mine).

Temporary Work (Short Stay Specialist) visa (subclass 400)

This visa lets you:

• stay in Australia while your visa is valid (generally up to three months, but up to six months may be allowed in limited circumstances)
• do short-term, highly specialised, non-ongoing work for which you were granted the visa
• in limited circumstances, participate in an activity or work relating to Australia’s interests
• bring members of your family with you to Australia, if they meet the requirements for including family members in your application. Your family members will not be allowed to work in Australia.

We will tell you how many times you can enter Australia on this visa.

Combining a holiday with your intended work or activity may be allowed if the holiday is of short term duration and secondary to the main purpose of your visit.