Some vehicles without modeled driver position, can move their view = hatch / vision blocks by pressing N- (zoom key) - sometimes deeper inside hull, sometimes nudge forward, or upwards. You can see this happening on video often enough as I keep pressing N key and numbat + key constantly.
Some vehicles with modeled driver position can have very poverful 2 level zoom by using N as is common but on top of that by hitting numpad + key (usually reserved for nightvision) This seems to happen mostly if not only on vehicles lacking drivers nightvision capability I believe (not entirely sure if I am correct or not.)
( Aslav25 driver can if well timed stick his head out when hatch closes xP )