The SBI PO Examination 2015 notification contains a list of tentative exam centres, the addresses of which will be given in detail in the call letters.
SBI states that it reserves the right to cancel, change or add any of the Examination Centres at its discretion depending on various factors.
SBI also mentions in the PO Notification 2015 that it reserves the right to allot the candidate to any centre other than the one he/she has opted for.
Here is the tentative list of Centres where the Preliminary Examination may be held. The centres for Main Examination may be limited.