This 2.5 billions will go out from our current forex reserve or do our military already have 2.5 billions in their account? This is not an either/or proposition - "forex reserve" is made up of the foreign currency BB takes away via financial institutions when an exporter, expat, investor, etc. bring money into the country and issues BDT in exchange. BB holds this foreign currency on behalf of the people so that it can be utilised efficiently for procuring goods and services from overseas. BB does not own this foreign currency and this money is not in the "budget" of any entity. At the point where BAF needs to make payment for any hardware import, DGDP processes this with BB via Letter of Credit application - DGDP deposits BDT to a bank and, subject to BB approval, the bank obtains forex from the forex reserve and pays the exporter. BAF does not get to obtain large amounts of forex from the reserve in advance and hold it for future use. At the point of finalising a deal, BB and finance ministry makes the final decision on whether the forex can be safely released without the reserve running too low. Coming to EFT procurement, the deal cannot happen without finance ministry providing final approval. They have only provided initial approval to proceed with negotiations.
It is unlikely that a multi-billion dollar deal without an extended payment plan (10+ years) would be approved.