I think the "argument", when the question isn't completely ignored, goes something like this:

Naturally deregulation and corporatisation will lead to lower prices due to higher efficiency from reduction in red tape and economics of scale. The undistorted free market will automatically provide more reliable and cheaper services. The magical invisible hand of purified capitalism will ensure all savings are passed on to whomever my audience is.

As for why that didn't happen? Oh, it's probably because of Labor. You know. Complaint about the renewable energy target goes here. That's gotta be it. Labor wants more blackouts.

Here's an economic model which by making dubious assumptions that require a bunch of handwaving and ignoring important issues you've raised as 'externalities' proves that letting corporations get away with whatever they want is good for you. This model usually works by giving a technical definition of some term that doesn't quite capture the natural language meaning (which is fine), and then making an argument about real-world impacts that relies on the nuances that were actually left out of the definition (not fine).

You disagree? Oh, well that means you're literally Stalinist and/or Marxist. There's no middle path, after all, if you question the value of privatisation, or even deregulation approaching lawlessness, well, you must be the enemy!