That article is pretty much correct, we still have three main gauges in use today. Those being 5ft3in Broad Gauge (mostly Victoria, and a small amount of SA), 4ft8.5in Standard Gauge (the interstate network is now entirely SG, plus all of New South Wales, much of South Australia, all of Northern Territory, and some of Victoria), and 3ft6in narrow gauge (Queensland, Tasmania, and Western Australia).
As above, the interstate standard gauge has meant that interstate services no longer face break of gauge. However, Victoria, Queensland, and Western Australia do face a change of gauge for goods traveling from interstate to various locations in the state (Victoria has converted some of the regional lines to standard gauge mind). This is done through either trans-shipping containers between broad and standard gauge wagons, or doing bogie exchanges in Melbourne (not sure if we still do this 'on the go' these days). Most loads that need trans-shipping would be loaded in containers to make doing so fairly quick.
Regards