Looking through the oneworld website, it has links to the various airlines' status levels and associated benefits. On each of the pages it states that these benefits will be received when flying on any oneworld flight. (The actual wording varies, but that is certainly the implication.)

Of the Emerald levels it has the following to say about priority boarding:
BA Gold - Preferred boarding at your convenience, regardless of the class you are travelling in.
QF Platinum - Preferred boarding. You'll be invited to board at your convenience.
Aer Lingus Gold Circle Elite - Preferred Boarding: To facilitate a more relaxed boarding procedure, irrespective of your class of travel when travelling on a oneworld member airline flight, Elite members will be invited to board first or at your leisure.
Cathay Pacific The Marco Polo Club Diamond - Preferred boarding at your convenience, regardless of class of travel.
Finnair Plus Platinum - Preferred boarding at the member's convenience.
Iberia Plus Platinum - Preferred boarding at the member's convenience.
LanPass Comodoro - Preferred boarding: they can board the plane at their leisure, once the process has started either before or after Economy Class passengers.

But AA AAdvantage Executive Platinum lists nothing about boarding.

Is priority boarding a standard oneworld Emerald benefit or not?

If so (and it seems like the intention is that it is), does this mean we are entitled to join the First/Business queue when on a oneworld flight even if we are down the back? Or do we need to wait to be asked?

I don't want to miss out on a benefit if I am entitled to it, but I also don't want to be caught out trying to use a priority queue if I am not entitled to be there.