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.
Bullet holes in transformers are common.
My younger son used to work in that stuff, and went out often to help bring them back up at strange hours of the night.
We have an abundance of idiots with high powered rifles, always looking for the worst possible targets.
Telephone cables are another old favorite for that crap.
The transformer windings are not vulnerable, as they have heavy vessels around them; it is the cooling exchangers that are necessarily made of thin materials.