To reproduce this place in the editor default NATO Weapons Sqaud and HEMTT Transport. Place "Get in" waypoint on HEMTT Transport, disable movement for all infantry except squad leader, start mission.
In 40-50 seconds after the start, the squad will be splitted.
Exactly the same happens with mechanized and motorised squads.
Place default NATO Mechanized Rifle Squad, place move waypoint 1-2km away, disable move for all infantry outside vehicle, start mission.
In 40-50 seconds after the start, the squad will be splitted and the vehicle will start moving towards the waypoint