If I understand it correctly, the deploy to template is always "building" around the nr 1 vehicle in the group.
If that is destroyed, the 2nd vehicle becomes the "nr 1" in the group, and the template deploys around that one.
Same of course for vehicles in the middle of the group.
So practical: You have a group of 1 command vehicle, and 6 artillery pieces, and you create a template with the command vehicle in a certain position and the arty pieces 500 feet in front of it on one line.
If the first unit (the command vehicle) is destroyed before they deployed to template, one of the arty pieces (the 2nd unit in the group) will take the position of the command unit, and the others will form a line like before. (-1)