All models can "see through" cover within a number of inches equal to their size. So in your example, if the hedge was within 4" of the PzIV's center point, and the PzIV is size 4 (I think it is, but I'm at work and so have no book handy) then yes the tank could fire through the hedge at the GIs. As Jayrider says, they would be obscured. The reverse is also true; a unit may "see through" an amount of terrain equal to the target's size score in inches. So if the GI's survive, they can put a bazooka round through that hedge, but the PzIV would also benefit from obscurement.