Obviously, this doesn't apply to the owner/operators who operate OTR and just come into the state on occasion but it would apply to trucks that are hired by the docks to work there. Granted, the period laid out by CARB for upgrades is over about 10 years, but with various deadlines laid out every few years by fleet size. This is how they plan to not run the little guys out of business. Still, none of this means anything to private non-commercial owners.
Dale, I think you've got it right there. The Port of Los Angeles is pushing to prevent major carriers from contracting out freight pickups to independents who have longer to upgrade. This way they get emissions compliance at large, sooner than later.
(The following is just my speculation
, I've not seen any stories suggesting it, but I would almost be willing to bet on it.)
If they get their way on this, the next step will almost certainly be to create a list of authorized carriers that are permitted to pickup or deliver at the ports, in the name of safety and security of course. To no small coincidense, few if any small operators will be able to afford the time and financial resources required to get on the approved list.