Tracerout gives me a path like this spine5.cloud2.fsn1.hetzner.com -> core22.fsn1.hetzner.com -> core5.fra.hetzner.com -> core53.sto.hetzner.com -> core31.hel1.hetzner.com
Which is worse than before, but still works for me.
I suspect that the costs of moving extra bits through other cables is not large. I would assume that Hetzner (and the other companies that own parts of these cables) have peering agreements with other companies and that most of them will not try and take advantage of the cut cables to renegotiate their peering agreements (2). So whatever rates they paid before will still be paid.
1: Because a war creates a problem for the risk pool, it is one of the things that actually can destroy huge amounts of property simultaneously, so it is a risk explicitly separated out and basically impossible to insure against, at least in the US commercial market.
2: Too risky to start renegotiating when your cable can be cut just as easily the next time.
UNCLOS Article 113 seems to say (to this non-lawyer) that the merchant ship operating country is responsible for punishment, and the only protection is if the mariners can prove that they "acted merely with the legitimate object of saving their lives or their ships, after having taken all necessary precautions to avoid such break or injury." Article 114 says that the merchant ship owner is responsible for the cost of repairs.
So that means, if it can be proven that Yi Peng 3 was responsible for this, then it's going to be on the Ningbo Yipeng Shipping Company to pay, and the PRC to punish. From what I have been able to find, that is a small shipping company with just two ships, one of which is currently unable to operate due to being stuck in the Kattegat. I suspect that means that not much money would be available from that direction, and so I wonder if the insurance companies would be on the hook for whatever excess costs are born by the various companies.