Vehicles in this game do not do that (from what I can see). I realized it was an issue when I had a tank at a 45 degree angle in a wheat field and tried to shoot at an infantry unit. Instead of a single -1 for the square between the two targets, I got a -2 modifier since the line was calculated from the center of the tank (apparently) rather than the front square. I understand this is an issue with the current UI and trying to keep the game play flowing, but it does lead to some surprises for players of the board game trying things that should be possible, but suddenly you cannot draw the line past the edge of a bocage.Whenever a two-space vehicle targets a unit, it can choose the center of either of its spaces as the starting point of its LoS.
Edit to add: Sorry I did not grab a screen cap. Basically, the tank was in a wheat field at a 45 degree angle, the enemy unit was 2 squares straight "up" from the front space of the tank. When I tried to shoot with the machine gun, both the space between the two, and the one just to the left (2 spaces "above" the back of the tank) showed a -1 LoS modifier.