I know it's an old thread, but someone might be interested:
As the new GRU-MPN-flight is now bookable there's a lot of award space for GRU-MPN currently. Bookable via LATAM Pass at 34.000 points r/t.
You can also book it with avios, but have to call BA for it. I did it yesterday and they only had Business space left for 39.000 Avios oneway. Quite a nice deal considering cash fares for Business Class are 2.000$ and upwards.
Interesting enough LATAM Pass only got Economy space while BA EC only got Business class seats.