In the case of the "Big Red", the bomb explodes, but does not destroy the semi-trailer. There is no way to "reload" the bomb..
In the "Jihad" cars however, they have unlimited explosions in them and do not self-destruct.. One could drive around the city with a collaborator in the passenger seat repairing and creating explosions..
Also, when the "Big Red" has no "ammunition" left/bomb has been used, there is an invisible "shelf" on the back of the truck extending from between the wheels/from the drive shaft.
I will try to get pictures of this "shaft" if possible.. It's hard to explain as I don't know how to describe the position of the "shelf".
This was all done on a local server.
Edit:
(Standing on the Ledge)

