Yeah having one's back already gives you the advantage to shoot down the target's weak spot. With the advanced sensors on the most units it is suggested that there is no true blind spot on the battlefield of Battletech. As long as you did aware the presence of the enemy unit, though(read = as you know ambushers does have the advantage for the pointblank shots). You cannot make the physical attacks as the pointblank shots, if I remember correctly, but it does gives some advantage for the shootings.