Hmm, not sure what this means but if it works I'm in. What's "private internet access" & "adding open VPN to router mean"? Can I get instrustions that a numbskulls like me can understand. I'm sooo missing may BF1!!!!
I managed to get talking to a supervisor (the agent I initially got was hopeless), and he confirmed the submarine cable issue is the cause. He forwarded me some details - relevant parts below. I also spoke to their billing department who promised some kind of compensation, but only when the issue is fixed (mid October!).
Engineering and Network team will try to minimise the impact as much as possible through re-routing via alternate links, however this will never be as good as the most direct "path" and so impacts as outlined are inevitable.
Thanks @JohnnyO for the extensive update - that pretty much matches what I was assuming. It looks like even when playing Battlefield 1 on Australian servers that some information is also sent to overseas servers (possibly user profile information). And that this works some of the time, but at other times the link gets so congested that the game gives up and drops the connection.
However it looks like other ISPs have figured out better alternate routing as it's only people on Optus that appear to be suffering from this specific Battlefield 1 issue, friends on other ISPs are still playing without seeing this issue.