Yes, same impression for me. I routinely motorize up the hubs in my allies lands if I join the fights in a region. I guess there is just a decision logic for the AI missing when to do it (or if there is one, it never fires because of some bug/suboptimal setting), though my feeling is that even it would fire correctly, there would be still the problem that an insufficient number of trucks overall is a common sight in the AIs arsenals - they just don't even have what they need to equip there divisions and in consequence exactly nothing left to theoretically/potentially motorize important hubs.
