When I visited Australia and spent some time there a few years ago, I was served Billy Tea. Billy Tea is a black tea blend. It reminds me a lot of Yorkshire Gold. It's full bodied, smooth and ever-so-slightly smokey. It's really nice, however, if given the choice I'd pick the Yorkshire Gold.
I also have a few other loose leaf black teas, but I find it's easier for me to offer comparisons to teas that are on the market and more controlled, like Yorkshire Gold.
Billy Tea is basically Australian Bush Tea. Years ago, early Australian settlers brewed their tea in a 'billy' which is a can with a wire handle. They'd fill the can with water, place it over the fire, add in the tea and bring to a boil.
When it's done steeping, the tea is served. Today, many add in milk or sugar. I take my tea straight though as I don't like to add anything to my tea at all.
When Billy Tea was served to me in Australia, dried eucalyptus leaves were added which was delightful.
I think the term 'Billy Tea' can apply to any day-to-day black tea. I associate it with Tetley's Billy Tea though, which is their registered trademark.
Anyway, you can find it fairly easily in the US now and most tea houses can ship it in for you.