nowhere to push branches for an initial upload to lucid-proposed

The plymouth package is maintained in bzr, and I'm doing the first SRU of it for lucid, so I would like to push my changes to bzr on LP directly rather than having the importer grab them after upload. There doesn't seem to be a way to do this, however:

$ bzr push --remember lp:ubuntu/lucid-proposed/plymouth
bzr: ERROR: Server sent an unexpected error: ('error', '<ProtocolError for xmlrpc.lp.internal:8097/codehosting: -1 >')
$ bzr push --remember lp:ubuntu/lucid-proposed/plymouth/lucid-proposed
bzr: ERROR: Server sent an unexpected error: ('error', '<ProtocolError for xmlrpc.lp.internal:8097/codehosting: -1 >')
$ bzr push --remember lp:ubuntu/lucid/plymouth/lucid-proposed
bzr: ERROR: Permission denied: "Cannot create 'lucid-proposed'. Only Bazaar branches are allowed."
$ bzr push --remember lp:ubuntu/lucid/plymouth/proposed
bzr: ERROR: Permission denied: "Cannot create 'proposed'. Only Bazaar branches are allowed."
$ bzr push --remember lp:ubuntu/lucid-proposed/plymouth/lucid
bzr: ERROR: Server sent an unexpected error: ('error', '<ProtocolError for xmlrpc.lp.internal:8097/codehosting: -1 >')
$

So at the very least there's a documentation issue, in that I can't figure out where I might be able to push this.

Fixing this might, however, require first that the SRU team and release team have some way to land branches into the archive by merging them rather than by accepting packages from the unapproved queue - since in general uploaders are not able to upload directly to -proposed anyway....