Last month I flew AKL-SIN-PEK-EWR on SQ-CA-UA in Business and I was able to have the bags checked all the way from AKL to EWR.
Now, I will say this required about 20 minutes at the check-in counter in AKL as they figured out how to make this happen. Then another 25 minutes at the transfer desk in SIN as we attempted to get our boarding passes for the CA and UA flights, likely from some creative work done to the record by the SQ staff in AKL.
In the end, our bags did not make the connection in PEK anyway, as the CA flight pulled into the gate at 4:30p for the 5:00p PEK-EWR, but we would not have had to reclaim.