Well the code from that blog entry works as reported for <directory> declarations but not for <location> ones where mod_dav_svn is the handler. I recreate both of those in a single server implementation if I mount the a svn/ folder inside the canonical docroot (as is common), then play with URLs that should be rewritten in the browser (or Wget) that are inside and outside of that svn/ sub directory.
For extra fun I moved the four rewrite lines before, inside, and after the Svn <location>, but it didn't make any difference. I'll try a straight handler next, in the hope that it can wholly intercept requests that would otherwise be routed to mod_dav_svn. - Paul