The oneworld site address is
www.oneworldalliance.com
Click on 'benefits' and then on the respective airline.
I think the problem is that BA doesn't have a 'Ruby' level. Rather it starts with the BA silver which is OW sapphire. So comparing to Qantas silver, which is OW ruby, causes the difficulties. I have found no problems myself using Qantas Silver/OW Ruby with AA as they too have a OW Ruby card (which is Gold in their scheme of things!). So really it is a problem with BA being a bit different.
OW // BA // QF // AA
No Status // Blue // Bronze // Ordinary card
Ruby // No Card // Silver // Gold
Sapphire // Silver // Gold // Platinum
Emerald // Gold // Platinum // Exec Platinum
Perhaps OW might convince the member airlines to commit to a plan to rationalise all these different levels to some more identifiable standard than a little blob of colour in the corner of the card.
I hope this helps.
[edited to try to fix table]