Firstly, app-shells/bash-completion already provides a contributed bash-completion file for subversion that is installed in /usr/share/bash-completion. That said, it sucks enormously compared to the one provided with subversion, so I will be editing the bash-completion ebuild so that it won't be installed. That takes care of the file collision issue. Secondly, please use bash-completion.eclass for bash-completions. Eventually it will integrate nicely with bash-completion-config. A diff is attached.
Created attachment 43767 [details, diff] subversion-1.1.1-r1.ebuild.diff
Thanks ka0ttic, I'll fix this up
All set now