The comment that made me chuckle was:
'First class demand can only be proven when BA return'.
Yes, me too. Actually, I took him to mean "if" BA return. i.e BA might return if they saw that there was a demand for First Class with other carriers that was already proven.
I've no statistics to back it up but my impression is that Business Class does well on a number of long haul routes from MAN - UA and DL to New York for example, EK certainly. Don't know about EY or QR. I suspect VS and CX do ok as well. And they can't all be due to frequent flyers or free upgrades.