Entries to the truck are virtually infinite.
Positions you can enter the truck from I can think of would be;
Side control opponent turns in
Side control opponent turns away gets to knees
Side control opponent turns away goes belly down
Back control
Deja vu (the truck to the truck)
Switching the truck
Passing the guard (double under pass)
Turtle
Sprawl
3/4 mount
Single leg td defense
The switch
Scrambles
Hip bump sweep counter