City sewer line collapsed, had $25K in damage, Texas law prevents city liability

I own an office building that I rent in a small Texas town. Recently I received a call from the renter that raw sewage was backing up onto the floor from the toilets. My contractor attempted to unplug the line, but after no success, ran a camera down the line and determined it was the city's main line that had collapsed. The city was called and confirmed it was their issue. I had to have flooring replaced, sheet rock cut, office furniture disassembled, moved and reassembled after the repairs, cleaning, loss of usage rent reduction, etc. At the end of the day, I had $25,000 in expenses and lost rent. The city provided me with a claim number to their insurance company, so I wasn't too worried. However, the insurance company called me back and told me that Texas state law protects city municipalities from liability from damages resulting from sewer lines backing up unless it is caused by a negligent city employee improperly using a motor vehicle. My own insurance company doesn't cover damage from this either.

I'm sure the answer is no, but has anyone had experience trying to get reimbursement for anything similar?