I was in a garrison(i had already scanned my surroundings), shooting an ARC through walls, before re-equipping my Lrn. terrain scanner. When it turned on, some of the green(scanned) dirt between the two walls wasn't highlighted like the rest because it was no longer there (because i had destroyed it by shooting it through the wall in order to reach the ARC).
I haven't tested it elsewhere yet, but i assume it does the same for walls and allows you to see whether they are still there.
On the topic of shooting ARCs through walls, one deployed upon death and the resulting grunts moved somewhat strangely when tracking me : four spaces at once, all at once(even when turning around corners). I assume this is normal but i just wanted to check. (i had FarCom)