I'm a community server admin. This issue has been found and confirmed during the administration of my ArmA 3 community server.

Battleye is unable to detect speedhacks. Every player can use an external tool like Speed Gear to manipulate the time in the multiplayer. This kind of tools accelerate the game time at the client side so that their moving speed (whether in a vehicle or not) at the server side (hence in other players' games) will multiplied.

This kind of hacks not only increase hackers' moving speed, but also increase the speed of the missiles (e.g. Titan AA) fired by them, which makes evading these missiles impossible, even with bunch of flares.