The outbound dialer in CCX 7 is a "direct preview" dialer. It is NOT a predictive dialer. Additionally, it does not have remote-end detection to determine what/who answered. That must be specified by the agent through CAD by selecting the appropriate classification such as voice, answering machine, fax, etc.
I am not at all familiar with the RightFax server (we sell XMediusFAX instead to customers); however, I can't think of how CCX would handle this cleanly. Anything is possible but I think they are looking in the wrong direction for this.
In the interest of trying to answer the question though: In theory you could write a CCX script that an agent could call into, specify a document ID that they want to fax, and the remote telephone number. CCX could then store this to SQL database through ODBC that RightFax could (?maybe?) read from and take action on at it's leisure. You would effectively be building a fax-back IVR. It'd be up to RightFax to pick up the action request out of the database though.