To my knowledge, a redirect to an anchor is not possible with just Apache directives. The anchor is handled on the client-side browser. Apache ignores any anchors attached to the end of a rewriterule (escaping the pound symbol has no effect either).
If you are working with a PHP-based site, your easiest option would be the auto_prepend_file
directive in php.ini. All you would need is a simple PHP script to read the current URL (if necessary) and perform a redirect to the new URL with anchor specified.
This type of solution should work for any server-side language with some adaptation. Sorry that I haven't seen an easier solution. Good luck!