The way the highway contracts are written — the contractor should be carrying insurance to pay for the costs incurred.
I don’t know California DOT contract procedures, but in a lot of Government contracts the Governmental body is self insured for property damage loss. This then comes under the type of Property Damage Insurance known as “Builder’s Risk”. But wait, there is often no coverage for the items that are not permenant real estate improvements.
For that, someone would have had to buy not only a Builder’s Risk policy, but also a rider often called an installation floater to cover the form-work and the false-works or centering support shoring that held it in place as it is not part of the permenant structure. The insurance might even say that the reinforcing steel bars we see are not covered as an uninsured portion of the Work collapsed bringing all the bar down into a bent up mess.
Insurance on these is a very nasty deal but if they bought a good enough policy the contractor could have the entire replacement cost and penalty covered. Likewise, the Government may say, it was not paid for, and thus CalDot property, we consider it your loss.