That still wouldn't mean that the crushed areas would have been empty. When the saucer did a forced landing in ST:GEN, a maneuver that it had been designed for, they had to evacuate sickbay, of all places! Lots of less critical inhabited spaces would no doubt have been at risk during the ramming, and specific evacuation orders would have been needed to make sure nobody was killed.
We can go two routes about it, really. Either Picard deliberately sacrificed a few hundred people because he feared/knew that alerting them would also alert Shinzon, or then he already knew the bow areas were empty because he had paid attention to the earlier damage reports that indicated the widest decks of the saucer were compromised and evacuated already.
In both cases, drama would have been better served if there had been some sort of a "revelation" about the status of those decks during or immediately after the maneuver. If Picard killed hundreds, that was his prerogative, and a heartwrenching choice that had to be made to save Earth - but we need to realize that the choice is being made, and sympathize with the hero. If Picard pulled an ace out of his sleeve, we need to be reminded that all things are so magnificiently working in his favor, that he is so cleverly exploiting the previously mentioned but cunningly underplayed fact that the bow has already been evacuated. We got neither of those revelations, which rather lessens the impact of the impact. For this rare once, more exposition (dramatically properly timed) would have been a good thing...
Timo Saloniemi