Visa certainly makes you to be eligible to stay in a region or across aussy based on the visa you are holding(190 or 189). Following the grant of visa, you can even work as a chef in a five start hotel with hige wages, although your occupation is telecom engineer for instance (ha ha ha).
DIAC won't look what are you doing after giving you the visa and hence you can roam around the streets of Aus.
You could work at Macca's if you wanted let alone another job category - DIAC doesn't really care what happens after you move here. As others have said, you could even open your own business.
The only work restriction is on federal government (Commonwealth) jobs, which are generally open to citizens only.
In the end, I ended up working in a different role from the one I had initially nominated (although it is related). It worked out better for me because I realised pretty quickly that I didn't want to work in my original role anymore! (At least not here.) And no, I don't work in IT.