Você pode encontrar as respostas na especificação da Lixeira do FreeDesktop.org :
Alguns trechos:
$topdir/.Trash-$uiddirectory is to be used as the user's trash directory for thisdevice/partition.$uidis the user's numeric identifier.The
$trash/filesdirectory contains the files and directories that were trashed.The
$trash/infodirectory contains an “information file” for every file and directory in$trash/files.
Não há referência ao diretório expunge , no entanto.