There are innumerous ways of reading the Network Analysis of the public transporation data of 2011+2012. For example between the adjacent Fatih Müze and Fatih Unkapanı busstops there are a total of 57 unique bus routes passing. Although the centrality analysis addresses Taksim and Kadikoy as the centers to the city this reading depicts Fatih as directly connected to environs in 57 separate connections. One comment would be that this is due to the existing greater city municipality on the spot.
Another finding of interest is that although graphs do not reveal geographic information the clustering of the busstops with conneceted bus routes form three clusters and this corresponds directly to the election zones of the city.
Considering only the departure and arrival stops we see that Kadıköy stop is far more dense that its two follower stops Taksim and Eminönü, which are in turn twice more than that of the next follower Kartal with 27 rotes.
With only Busroutes Taksim and Kadıkoy champion as the central destinations. (Centrality denotes given any two destinations the node that you might end up passing) however once metro and ferries are included in the graph we get a fairly distributed centrality where still Taksim and Kadıkoy champion with Fatih following you get a few more central districts. Isolating busroutes with ferries AND busroutes with metro shows us that ferries are effective in the centrality distribution.
In a only-district based mapping we see Fatih and Kadıkoy as districts most central, and Taksim(Beyoğlu) as district losing its centrality even behind that of Esenler and Eyüp.
Here is the Turkish document regarding the above.IstanbulToplu.2012