As I understand it, BN pays a royalty to all artists/estates for everything sold. It is the responsibility of the artists/estates to inform the label of their current address and rightful status. Remember Tom's story about finding Jutta Hipp and delivering the check. Musicians "always" say they don't get anything.
Believe me, deciding where to send the money is no easy question. I have had problems and I only started my label in 1967. I have at least 4 estates in dispute, and only 2 have contacted me.
The above concerns "artist royalty" only - composer royalty is automatic to the Fox agency and they must hold tons of money waiting for the correct address/heir.