It’s the cooling oil that has to be replaced, not the transformers.
If there is no cooling oil, the transformers may have a meltdown or damage.
They can be taken offline and power re routed, but if this type of incident happens in many such locations simultaneously, the power outage could be long lasting.
Maybe cases could be patched, but I’m thinking more likely new ones are called for — also, we don’t know if the bullets reached the inner transformers themselves. It would be foolish to assume not without careful inspection.
It probably will pay to have a live guard at the station in the future.