When running as root, tar will properly set the owner and group of extracted directories and files. However, for symlinks, it uses root.root. The chown and chgrp commands do operate on the symlink, itself, and not its target, so it is possible to set the ownership properly. The symlink owner.group info *is* in the tar archive, so that's not the problem.
linux versions prior to 2.1.86 didn't include the lchown syscall, which allowed changing ownership of a symlink itself, instead of the file it points to. While it may have looked like the ownership was changed, the behaviour was undefined. GNU tar doesn't handle symlink ownership well. however, it does support lchown. In Red Hat Linux 6.0, which will ship with kernel 2.2.x, this means that ownership of symlinks is correctly handled.
for more information, please see tar's README file.