I'm told that SQ have been doing similar freighter patterns for years with some very good loads from the US into Europe. They take about 10 days over it but that includes an extra stop in Asia which CX don't need. Also SQ don't have based 400 crew so the same people do the whole pattern whereas CX have other options available.
Interestingly SQ also normally route the return NYC non stop flight across the Atlantic for a shorter flight time.