The first video is a Russian Engineering Battalion equal to a US engineering Company in personnel.

The Second is a Russian Armored Infantry Battalion equal to a US infantry company in size

The third video is a Russian Tank Battalion slightly larger than a US company

The forth is a rocket Artillery battalion about the size of a MLRS battery but no where near as accurate or destructive.

In total this is 1 Russian division minus ADA and support troops.

The passenger cars carried the personnel assigned to the units. Russian doctrine is send their equipment with a full combat load of ammunition and equipment and to have the personnel with the equipment in the event they need to offload and fight as quick as possible. US forces ship their equipment without ammo or light weapons and the personnel follow in either a special train or plane.