The citation that it works is in the article.

Regarding the ROI and subsidies, I guess you would need to compare them to the billions received by the incumbents :)

The power crisis in South Australia has been extremely costly. The cost for the proposed fast start gas power plant was 380 million.

The state-wide blackout cost businesses 367 million.

http://www.abc.net.au/news/2016-12-09/sa-blackout-costs-coul...

This battery will cost taxpayers 50 million over 10 years, apparently. Seems like a pretty good deal.

http://www.abc.net.au/news/2017-12-01/tesla-giant-battery-of...