Yes, BA allowed me to ticket ARN-MAD-LIM-SCL-PUQ-SCL-GRU//GIG-SCL-IPC-SCL-CCS-SCL-AKL-... on a LONE4, with a confirmed price and everything. They didn't know where IPC was so I got SCL-IPC-SCL at no extra fee. They only did count $150 extra for SCL-CCS-SCL which means I had 10 segments (as they beleived that intercontinental segments count in the continent as well) but I only had to pay for 2 extra, that is 6 segments in SA for free, 2 that I paid $300 for and 2 that they didn't know what to do about. Unfortunately my TA found out as she rechecked everything, but it did get priced and accepted by BA (she had talked to the BA TA CS).

Unfortunately, the ppl at BA seem to have no idea about the product they sell. I also spoke to Finnair and they said you can have max 4 segments per continent, and that it was impossible to buy extra segments.
The OW-carriers seem not to know the products they sell