I've recently been looking at LAN fare classes for earning on and have been amazed to find that even a £400+ return ticket on an Argentine domestic ticket doesn't earn a single Avios or tier point. This in not for a last minute ticket either but one for travel two months in advance.

I wonder why this is considering the vast amounts of tier points you can earn on the likes of a AA domestic? LAN tickets seem to be the stingiest out there for earning on yet are amongst the most expensive.
Is it LAN who make the rules or is it BA who decide what the earnings should be in relation to fare class when flying with partners?