1. okay, and if it wasn't them, then what? If it was the freshly elected councilors, see points 2 and 3
2. No you spoke about democracy, as if it's defined by the DA's constitution (why else in your view are party members obligated by democracy to vote according to party lines?) 
3a. What constitutes new info? You're in an impossibly grey area. T A secret ballot is a secret ballot.
3b. Last I checked, secret ballot for electing a leader is the established principle. It's the principle of secret ballot for vote of new confimdence that has only just been established (though not yet employed), giving the ANC a better argument than the DA's.