I don't think the LAV-AT issue is caused by an underlying problem with the LOS system. I setup two further missions with the roles reversed: a bunch of blue vehicles at the one end of the map and some Syrian militia forces at the other, so no NVG present. In daytime the Syrian forces immediatley spot the blue vehicles. In the night scenario they don't spot anything. LOS for the Syrians stops at the same 400m as for the LAV-AT. This does seem to point to the LAV-AT missing IR optics.
I noticed this as well. I think that ther is a bug with tha LAV-AT in that it is missing it's IR optics. I built a simple mission in the editor with a bunch of Syrian vehicles at one end of the map and some LAV-AT's, TOW humvees an Canadian LAV TUA and a few unarmed vehicles at the other end. The two sides are about 1100 m separated. The weather is clear. I ran one setup at 11:00 and one at 23:00. In the mission at 11:00 all the TOW equipped vehicles immediately begin spotting the enemy vehicles. The unarmed vehicles spot the enemy fairly quickly as well. In the night mission the TOW