Yes, you save 10k in Y and 20k in J. I did the other way round because I was en-route to the States on SQ2, and had to visit my friend in Bangkok back then. Hence I decided to start SQ2 at HKG, since SIN-BKK-SIN-HKG-SFO sounded pretty dumb, so did SIN-HKG-BKK-HKG-SFO. This was however done using AM instead of Avios, you gotta call BA up to see if they could ticket such an itinerary. Even AM can't issue the ticket online, you gotta call their agent as well.
Does your company have some special fares with CX

I actually dislike flying on CX for any route other than HK/USA because of the connection. Unless I want to include HKG as a stopover, I would usually find a direct flight.