just to remind me later :_)
duplicity restore \
--scp-command 'scp -o IdentityFile=/home/phaidros/.ssh/id_rsa_duplicity' \
--sftp-command 'sftp -o IdentityFile=/home/phaidros/.ssh/id_rsa_duplicity' \
--file-to-restore path/to/folder scp://user@host.mybackup.de/path/to/backup/ \
localfolderforrestoredfiles
now, profit!
:_)