I have a git repository which tracks an svn repository. I cloned it using --stdlayout.
I created a new local branch via git checkout -b foobar
as of git v1.6.1, git svn branch is available.
From the git docs:
branch
Create a branch in the SVN repository.
-m, --message
Allows to specify the commit message.
-t, --tag
Create a tag by using the tags_subdir instead of the branches_subdir
specified during git svn init.
Previous versions of git do not provide a way to create an svn branch.