So.. does this mean that if I am travelling to London for work, and I can only travel Qantas, then it will no longer be possible for me to buy a ticket that transits in HK? This makes the oneworld alliance seem like a very loose alliance indeed... 

My guess would be that more than half of business customers going to Europe go to London. Under the BA arrangement, I would be able to go via Bangkok, HK, or Singapore and still get full status credits and points. Now the only option is Dubai (which I think is less desirable a place to visit more than once than any of the 3 existing cities)...

It is situations such as yours that will cause a lot of people in a lot of companies to become somewhat agitated - and perhaps consider new alliances and carriers. Interesting times ahead for QF competition.

No QANTAS have stated you will be able to transit through Asia if you please 

You will still be able to route through any of those cities, and earn SC and FF points if it is a oneworld airline you have your connection on.  You will miss out on the status credit FF point offer if you are high status FF.  However, this is not a feature of oneworld, QF, AA and (formerly) BA offered this as something extra.  So the OW alliance will still give you a fair bit.

Will I be able to book these tickets on the Qantas website?

This was one of the most sensible options to places not served by Qantas in their own right and they threw it all away for some silly Emirates deal that for most of us is a no go zone into and out of Europe for Religious and other reasons.I have yet to do another Europe Trip but If I had to choose another non Singapore stopover It would be Hong Kong for the fact it's pretty easy to get about and safe too(Not as simple as my other option though but a lot nicer than Dubai).I can see Cathay Pacific and all of the other Asian Oppositions rubbing their hands with happiness winning over new customers.