I am not a plant expert, but what I am gathering from above is that you could dig a hole in the ground, drop the entire thign in pot and all, cover with a layer of mulch like you would normally do when planting, and then pull it up pot and all in the spring.
I am in South Dakota, the ground freezes hard here too, but it certainly isn't impossible to dig into. We had broken out the jackhammer in February to dig an egress window well hole, but I can't believe your ground is frozen so hard now that you can't dig a pot sized hole.
It looks like you have a fair amount of money into those plants. Hire a temp worker to dig some holes for you if needed.