Tier 2 introduces vehicles for both Species. The presence of vehicles can create a distraction for players to deviate from pushing into or defending Territories, or prying the Core from the Defenders' strong hold. And when forged correctly, Defenders' vehicles can represent secondary Objectives for the Invaders.
While from the Game Type's perspective the six teams continue to operate as six individual teams, the game play changes somewhat when players begin to operate vehicles. Their scope of influence can increase dramatically, their ability to travel across distances of the map increases, and usually their ability to enter into the enemy strong hold is dramatically reduced. And vehicular play will shift strategy from relying upon a numerical advantage to one of heavier fire power.
For Tier 3, Invaders who take up vehicular play can hinder their side from extracting the Core, when the Core is deep within a fortified structure. In these cases, the Invaders need every man in the building to neutralize the Defenders long enough so that they can pull the Core out the door.
Defender vehicles usually spawn in a reinforced (read that electronic fence) garage to prevent Invaders from jacking them from their spawns. Invader vehicles usually spawn back at their initial spawn locations, using the sheer distance from the Defenders as a natural obstacle to jacking at their spawns.
But Spire is different. The Banshee is the Defender's only vehicle and a very powerful weapon system. It spawns in the open, readily in reach of the Invaders. It acts as a secondary Objective for the Invaders, leading the Defenders to either split their resources to protect the Banshee, or abandon the Banshee altogether and hold up in the Spire to camp the Core. This is yet another form of divide and conquer. Without the Banshee, the Elites really have little chance of stopping the Core if it were to ever get out of the Spire and down on the ground. But if they successfully camp the Core, then having all the vehicles on the map won't do the Invading Spartans any good at all.
Vehicles tend to pull players attention from capturing or contesting Territories, and make subtle, yet very real changes to the way the Tier plays.
For Tier 3, Invader vehicular play can actually hinder the Invaders from extracting the Core, since the vehicle may be in use too soon.
The Defender vehicles could be used as secondary Objectives to provide Invaders with new divide and conquer strategies.