Actually, censorship is nothing new for Turkey so some serious portion of the population knows how to overcome it. Probably these tweets are sent mostly by Turks in Turkey :)
However, this is not the whole story. The current ruling party has huge support from the uneducated and/or religious masses that may not be that informed about the technology. Since 3 months new corruption documents are leaked through twitter, which puts pressure on the PM. Just yesterday there was a phone conversation of one of the Ministers leaked and apparently the guy was mocking Islam when he was trying to look like as devoted muslim in front of the public.
