How is it legal for them to take scooters then charge scooter owners for them?
Looks like they only remove scooters that are being left on private property. I would think its completely legal for the land owner to remove the scooter, therefore having another service remove them for you and charge for storage would be fine as long as the rate is not extortionate.
Because anybody can use and park the scooters, I would think it's in somebody's incentive to move scooters from pubic sidewalk onto patrolled private property to get scooped up.
TBH, I'd also trust an established towing business to handle scooter pickup, because scooter pickup would not be their only line of business, and they presumably wouldn't want scooter shenanigans to affect their towing business.
There's nothing new here.
Stores have several alternatives to this:
• They can send employees off-property to pick up carts they find. I used to see this in the past; not really as much anymore.
• They can install an "invisible fence"-type system, which causes one of a cart's wheels to lock up when taken outside of the permitted area. If you walk to/from the store, you'll have seen signs warning about this; otherwise you can check the carts to see if one wheel looks different from the others. The Safeway near where I live does this.
• They can require that customers pay a refundable deposit to use the cart. See the "Why do I need a quarter?" question at https://www.aldi.us/en/about-aldi/faqs/about-aldi/ for an example of this. This doesn't happen in the US much.