|Then maybe they're not supposed to.|
I just looked at a WRT54GL running Tomato and the remote access page shows you can remote access via http and ssh and can even designate allowed IP's. But there's nothing for remote telnet access.
I suspect it's not actually supported.
Any reason not to use http? I know the ssh/telnet interface on these 54GL's is nothing to write home about and I doubt you could make changes in it's config from either ssh or telnet so you'd likely be better off using http anyhow.