About the only telnet you can do is for Network Remote control.
What are you wanting to do? Download Video? That is possible with different software like Tivo Desktop, or PyTivo, KMTTG or even just using a web browser "HTTPS://" + your Tivo IP + "/Nowplaying/index.html"
Password: your Media Access Key
Original S1 (Recycle Heaven)
Series 2 (PLS, sold)
TiVo HD (XL, PLS, "652")
Juliet Basic (4XL, PLS)
The TiVo Apocalypse begins on Sat 2013 Feb 16 00:00 GMT!