Hi Tim et al,
Good question. I have been wondering about it too. I can't say I know anything more about it... but below is an interesting link on Aussie current. Apparently, our old friend Alex Ward (or Val Robertson) might be the best person to clarify this issue.
For information on Aussie current http://aussiecurrent2012.blogspot.jp
For information on Russian current, your home page at electrotherapy.org is a good resource. http://www.electrotherapy.org/modality/russian-stimulation-and-burst-mode-alternating-current-bmac-
Hope this helps... other replies much appreciated.