Question for 2011 Southern Sudan referendum

As part of the 2005 peace deal ending the Sudanese civil war, a peace treaty was signed which called for a referendum in 2011 to exercise the "right of self-determination" of the "people of Southern Sudan".  The provisions for a referendum can be found on page 8 of the treaty. http://www.aec-sudan.org/docs/cpa/cpa-en.pdf (you can see that page 8 of the treaty was subject to some last minute cut-and-paste, as can be seen by the misnumbered sections).   The two options of the referendum, according to section 2.5 of the treaty, will be "to confirm the unity of Sudan by voting to adopt the system of government established under the Peace Agreement; or to vote for secession."