If I'm travelling on Biz class on CX, can I gain access to other Oneworld lounges with just my boarding pass?

It's not something I'd rely on. Reports here have been that experience varies. We might be able to help more specifically if you told us which lounges. And I can't think of many places where other OW J lounges are accessible and preferable to CX's. (The old Singapore lounge was one, but I guess that the newly opened CX lounge, which I haven't seen yet, is at least comparable to the BA/QF lounge there.)

How about the Qantas lounge in BKK?

Ops-up does not include lounge access right?? That's what the lady told me at SIN

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I got op-uped at check-in... The lady at the lounge said that op-ups have no lounge access. I was at SIN

But you would get access in CX lounge if you are Ruby on Asiamiles, or Sapphire or above OW, regardless of class or ticket your holding.

I am only a lowly silver and my brother whom was travelling with me got an op-up also. So my brother doesnt have lounge access and I am unable to bring him to the lounge.

Then you first OP is misleading, you are not Travelling Business Class you are Flying Op-up Business Class on one sector. Your are actually travelling and have paid Economy. Please post the correct facts in your OP.

PS and you will not get Business Mileage either.

Silver on MPC gets you access into the MPC lounge when travelling on CX flights but you cannot bring in any guest. That's probably the reason why.

The flight that I was op-up and the flight that I was travelling on business class are 2 seperate flights. In my original question, my question was, I paid for business class fare, I would like to gain access to other OW lounges, is this possible.

Then somehow the topic of op-up was brought into the picture. And my new query was "Does op-up that was done at check-in entitle u to full business class lounge access. According to the lounge lady at SIN, op-up at check-in does not entitle u to lounge access."

CX policy seems to be no.
I had double op-up to and from SIN and first time every on CX, went to the Pier and was thrown out (looked like an idiot). Then I asked the lady at check-in kindly and they said unless you paid for it or with Status.

YOUR INFORMATION IS JUST PLAIN WRONG

*A rules say a j pax can enter any *A business lounge OW has no such rule!

Well if you go to the OneWorld timetable downloadable from http://www.oneworld.com and look in "Information/Lounge Access" then it appears to state what marcuslai says. There is slight ambiguity in that it only implies access to all oneworld lounges rather than explicitly states it, but I would certainly read it as marcuslai does.

(Unfortunately I can't copy/paste the text from the oneworld timetable and I can't be bothered to retype it all!)

The following quotation (the remainder of this post) is from the oneworld timetable, valid August 5, 2005, through September 2, 2005, in the section entitled oneworld benefits.

Lounge access by class of travel

Customers flying First or Business Class have access to the equivalent class of lounge regardless of their frequent flyer status. (First Class passengers may be accompanied by one guest traveling on a oneworld sold/operated flight.) Customers flying in Economy class on the domestic or intra-European segment to connect to or from a oneworld longhaul First or Business Class flight can also use the lounge applicable to the class in which they are travelling the longhaul segment.

Access is available on the day of departure when your next onward flight is with a oneworld member airline. Access may be restricted at a limited number of third-party lounges or due to capacity constraints. Arrivals lounges are not part of the oneworld lounge policy. American Airlines and Qantas offer programmes enabling a customer to pay to gain access to their lounges. These programmes are not part of the oneworld agreement, and members of these programs are not entitled to access lounges under the oneworld agreement.

Exception: American Airlines AAdvantage members, regardless of their tier status, may not use lounges when travelling on solely North American itineraries (defined as within or between the USA, Canada, Mexico [except Mexico City], the Bahamas, Bermuda and the Caribbean). In these cases, access rules are governed by American Airlines' own rules (ie paid lounge-access membership).

Note:
All oneworld benefits are only available to passengers on scheduled flights that are both operated and marketed by a oneworld member airline. (Marketed means there must be a oneworld member airline flight number on the ticket.) LAN ECUADOR is not a member of oneworld and does not offer any oneworld benefits.

the scan of the sheet the lounge dragon in lhr uses shows status only as a way to enter the lounges.

if this were true, if finnair called the front cabin F like AA calls its front cabin on short flights i.e lax sfo then one would be able to get into the first lounge in lhr by flying finnair for a short flight?

you must use the lounge of the airline your ticket is on if your using COS to get in. if it is status, you can lounge hop.

hkg is an exception to this rule they will allow ba f pax into the f section of the wing, i am sure there are other exceptions but as far as i know its just hkg