I actually have seen this, although the fire was contained to the inside of a metal enclosure so minimal damage was done.
This was in a 6-plex condo block. The garages and utility closet were on the bottom level, then the kitchens and living rooms above that, then the bedrooms on the upper level.
What happened is that the fridge ice maker in the unit directly above the utility closet was leaking for quite some time, which was dripping into the 6-pack meter array. When I was called in, the fire department had just been there responding to a fire alarm. One of the main breakers was melted onto the main bus (literally) and had been smoking enough to set off the closet alarm. Apparently, there was enough water to arc across the legs at the top of the 2-pole breaker.
There was severed damage to all three of the main breakers in that section of the 6-pack and the insulation on most of the wire was damaged, some to the point of exposing copper.
Funny thing was, all three of the units had service! None of the breakers, even with the arcing, had ever popped.
Had this occurred in a different type of enclosure, we may have seen an actual home fire caused by water.
BTW, Merry Christmas everybody!