"It is not a separate company"
CX refer to CX Cargo as a subsidiary or a separate business. It is operated independently with different accounting, tax write offs and business model to its parent.
If CX Cargo, SQ Cargo, Emirates Sky Cargo and MOST other cargo divisions around the world were deemed to be profitable within the structure of the parent company, then they would be operated that way.
But they are not.
The point being, QF mainline will NEVER operate cargo aircraft within its mainline cost structure.