How is it that you are so sharp on this?
I know of a lot of these rules from my work. I work as a tax accountant / administrator for SMSFs. Not high up or anything, but I keep an eye out for any ATO updates. Read enough of them, and you begin to know where to look. I'm no expert, but find that discussing some of these things enhances my knowledge.
As far as I know, the secondary market for "cum div" stocks was set up by the ASX to allow foreign investors who could not claim the franking credits because they were not Australian residents.Yeah, that div washing stuff is all linked to options creating a cum-div market for a few days around ex-div as calls are exercised. And then the hole was found and exploited. I would never have dared do this sytematically. But across the line for the ATO and way beyond the intent of the Act and any conceivable concept of 'incidental purpose'. Took years for the crackdown to occur. It's just an example of how much you can push the law beyond what is written before the ATO bites.
Cheers
Of course, others saw an opportunity in this. The ATO is often slow with this stuff as you said, but when they catch wind, the door gets jammed shut pretty quickly.