Subject to an election under section
8416
(a) of title
5, and unless otherwise expressly provided by any spousal agreement or court order governing survivor benefits payable under this subsection to a qualified former spouse, such former spouse is entitled to a share, determined under subparagraph (B), of all survivor benefits that would otherwise be payable under subchapter
IV of chapter
84 of title
5 to an eligible surviving spouse of the employee.