I have asked this on the CGL discord but I wanted to post here to double check and as a reference for future folks who have the same question.
RAW, in order to dismount transported units, you must first activate and move the transporting unit. At the end of the transporting unit's movement, you can choose to have any number of its transported units dismount and move up to half of their mv and shoot.
As I understand it, immobilized units do not get activated during the movement phase.
This raises the question, if a transporting unit is immobile, does that mean that it can't dismount those units since it will never get an activation? For example, if the transporting unit is a vehicle that got immobilized via a motive hit. That vehicle transport can never dismount its units for the rest of the game, RAW. Is this intended, or am i missing something that lets the transported dismount if their transport gets immobilized.