LATAM flights do NOT earn Tier Points or Avios with BAEC, when booked as an IB codeshare. Note the chart below - this is the case of "marketed by Oneworld, operated by other airline"

https://www.britishairways.com/en-gb...avios/flights#

You're not going to get anywhere near IB+ status with one return from South America to Europe, but it's the safest way to earn Avios. No idea about LATAM Pass.