If they're oil cooled transformers then they do have a tendency of catching on fire. It won't take half your street out but I wouldn't want to be 15 feet from one that's on fire.
Of course if one gets hits by a meteorite and catches fire then keep a safe distance. Definitely more than 15 feet. In normal operation they are extremely safe though.
A hazmat crew in full bunny suits showed up to clean up the mess. The story I remember (this was a long time ago) is that PCBs were present -- I think they stopped using PCBs in these things since then -- and that was why the hazmat team was needed.
It was quite exciting, though, and remains a vivid memory.