Oddly having had my ticket re-issued they changed the plane to two class (I was on a AONE5), they offered my MCO's for the downgrade which is not in the OneWorld rules.
The staff at SCL and Rio told me that I could cash these at any ticket office.
Upon presenting them at JFK I was told that they had to be sent in to Miami for refund.
Well after several months of waiting (3 months from submission), I got a cheque in US$ from Lan, so I am pretty delighted and it will pay a good part of my 2005 AONE5.