Thank you everyone for the suggestions. We've decided on what we're doing to protect the baskets, so I wanted to share. These are Gateway Titan baskets and the sleeves attach through the pole, very different from the baskets I'm used to.
1 = welding the nuts/bolts that attach the basket to the pole
2 = filling the entire pole with concrete. We'll assemble the baskets, cap the top, the sit them upside down and pour concrete into the pole right up to the hole where the sleeve attaches
3 = drilling out the holes through the sleeve/pole to 5/8" and using 5/8" diameter trailer hitch locks
4 = using rebar into the ground and extra concrete when setting the sleeves
These should be incredibly secure. And the Gateway baskets are extra beefy, I've got one assembled and it weighs 70 lbs vs 56 for my Chainstar ... that is pre-concrete-in-pole weight
I hope someone in your work crew is big enough to heft them around once they're filled with concrete. I guess the extra weight is a feature of the theft deterrent?