don’t know how your package is configured, but mt-daapd has it’s own mdns responder built-it, or it can use howl. I don’t know how your package is configured (if it’s the Sarge one, it uses the built-in — don’t need mdnsreponder).
wrt seeing across a tunnel — the mdns won’t tunnel. You’ll need a mdns proxy. Check the faq page — that gives links to some different proxies.