Current initscripts in F15 installs fedora-storage-init-late.service but creates no symlink for it. The package should probably create a symlink for it, like it already does for fedora-storage-init.service in /lib/systemd/system/local-fs.target.wants/
Oh, and I think it would be good to place an "After=fedora-storage-init.service" in fedora-storage-init-late.service in order to not run vgchange twice at the same time. LVM might not choke on it, but I'd rather not risk this.
Oof, not enabling it was just an oversight. Fixed in git (along with the After= line), will appear in a build shortly.