I dare to disagree. Right now very fast ship can penetrate your radar coverage without detection and attack your base without warning. Entire purpose of radar system is to detect enemy and give you early warning, so this obsolete game machanics strips radar of its purpose.
Well like Dioxine alluded to earlier, if the attack ship spawns within your coverage area you'll spot it. Granted it will be moving so fast you won't be able to do anything about it except maybe to evacuate your troops but that would be kinda silly. So I guess my point is that even if you did spot that incoming attack, it's far to late at that point. You would have had to shoot down the initial crackdown ship to stop the boarding torpedo from launching in the first place (assuming that's what spawned the attack, there's other factors at play).
Edit: Also in the newest version, when you try to shoot a spotted enemy and you don't have a shot, the tiles that are blocking you will blink a couple times. (really cool addition btw).