A lot of the special effect CGI models were taken directly from assets made for Halo 4's own in game cutscenes. This can lead to some minor Continuity Snarls if a viewer is being picky.
Cadmon's ODST armor (along with other ODSTs shown) is reused from the live-action short "The Life", also known as the "We Are ODST" commercial for Halo 3 ODST.
The armor worn by Kelly-087 and Fred-104 are modifications of the armor worn for the Halo Reach "Deliver Hope" commercial. Amusingly enough, one of the helmet's modifications was attaching the prop of an armored knee plate over the bottom of the visor.note (HaloCosplay enthusiasts had quite a chuckle when they saw the helmet◊.)
All the warthogs shown are the same prop with different modifications. This prop warthog is a fully functional vehicle made by WETA for the long-abandoned Halo film. It was also used in the Neill Blomkamp short "Landfall" to promote Halo 3.