All the etags you can get down here in Melbourne work on all Melbourne and Sydney tollways.
The old ones are big and clunky, and look a bit like this:
The new ones are much smaller and easier to mount discreetly:
It's interesting that Eastlink/Breeze say this on their website:
We know that the tags most people have are too big and bulky, and many people like their car to look good. That's why we've worked with designers in Melbourne and Sweden to create a new tag design that's exclusive to Breeze. The Breeze tag is the smallest tag in Australia, and probably the smallest in the world.
Breeze tags have an easy-to-use holder for attaching the tag to your vehicle's windscreen. Once attached, the tag can be easily removed and replaced. Tag holders are free of charge.
Which is rubbish. The new tags from Citylink are almost identical, just a different logo on the case.