For objective B, which is located inside the back of a police vehicle, a Sniper is stationary on a building a distance away (where Objective C is located), overlooking the police vehicle. It may be possible, if taking an alternate route, to distract the Sniper in order to make it easier to scan the files and quickly get out.
There are three ways to get to the next area (where Objectives B and C are located) at the start of the missions: the path to the left takes you through a building (where Objective A is) and a small minefield (which can be bypassed). The middle path, while possible to move through, is the most risky as there is little cover and more guards. The path to the right leads up to a rocky area where mines, a High-Value Target and security cameras are located.
behind the first builing (wich "A" is located) there is a switch witch turn of the cameras in the first area and can be accesed by a dual breach door or through the building.