I'm not sure if this is what you are asking, but 22.214.171.124.1 states that dismounting a towed unit expends all movement points. They are deployed in the same hex as the towing unit and can face any direction. I believe unlimbering the towed unit is part of the deployed process.
It then says that the towing unit expends half of their movement points in the process. So to me, I think those costs are accounted for.
When mounting/dismounting, does the passenger unit always spend his Move command in addition to the vehicle spending it's Move points to do so? Or is it either or: the unit can use its command to mount or the vehicle can take the cost of the mount/dismount?