Yes, it seems Westpac are the only competent and helpful retail...

Yes, it seems Westpac are the only competent and helpful retail local/global brokerage in Australia that are able to get this done.
Service levels at Westpac are notably better than at others I have tried.

One set of my Westpac shares has been sent directly from my Local Westpac HIN account to HSBC custodian and HSBC has confirmed receipt to me. (2nd leg of ADS conversion and redeposit into my international account yet to be completed, but I do not expect any issues)

(ie no HIN->SRN conversion and Boardroom form required)

But how is that US tax treaty: Anything you sell, if we don't like your certification we will just take 30% for ourselves! Not 30% of profit... 30% of total sale value! Good luck challenging that!