Cathay Pacific will do select status matches on a case by case basis.
If you hold Silver equivalent or above status with other carriers and plan to fly CX or KA a lot, it may be worthwhile to get a status match. However, I believe this will only be matched at the Silver level. You’ll still need to earn Marco Polo Gold and Diamond the traditional way.
The best benefit of Marco Polo Silver status is the Cathay Pacific lounge access which you do not get as a oneworld Ruby member. There’s other benefits as well, such as additional baggage allowance, see full chart here.
To request status match e-mail: firstname.lastname@example.org
I would include a copy of your current membership card, and a statement only if you rack up tons of mileage. I’d probably include a short written message explaining why you want the match and record locators of any upcoming flights if you booked those, revenue tickets of course.