I suggest using a pair of snips to cut the supports holding the carts but carts can be removed by hand with some amount of rocking and twisting if done carefully. The supports attached to the wheels are the most likely problem spot. I suggest pushing against the wheel with your thumbnail to hold it in place and then bending the support to break it off from the wheel. But using snips is best.

There is a possibility that these carts will become more flexible from having wet paint applied to them and that the baskets may sag. I suggest tilting the cart on its back to dry after painting so that gravity doesn't cause the basket to sag while the part is wet. No one has complained that its a problem, tho, so it's prolly fine.