Sure, but I think people throwing things into the canal is unrelated to the points raised in OP or by me.

Similar situation happened where someone kept throwing outdoor chairs into the canal from Biraria (a restaurant located near the canal in Malmo)[0], the municipality made them pay for it and it sent them out of business (those trawlers are expensive).

Tugg, the place that leases the space now; has insurance for this.

I don't see these cases as dissimilar.

[0]: https://goo.gl/maps/E2XraNA9Yxx9mic7A

Insurance would work if the e-scooter companies paid for it. You can't however use a trawler as that would be counter-productive if the concern is ecological damage, so it would need to be commercial divers which is quite expensive when dealing with low visibility canals. The insurance premium would likely be quite high. The companies can naturally try go after the criminals in order to recover the costs.

The two issues are however related. Commercial operations need to pay external costs imposed on the city from commercial activity, be that parking issues or water pollution. If companies refuse to do so it will be up to the citizen to decide if they want those costs be paid through taxes, or issue regulations that may force those companies to go out of business. Either way someone will have to pay for cleanup. Right now no one is doing that in Malmö and other Swedish cities, which is not sustainable.