Fires are not cause by the mining machines themselves, they're usually caused by non-electrically trained people overloading the electrical capacity of their cables, or people not maintaining their equipment and cleaning the dust out of it.

Well, I have seen GPU capacity burst out in flame, although its not long but if the fire catch something else then its gone..
GPUs are not equal to ASIC mining rigs.
One thing is bugging me about the recent fire: Why is ~5% of the world hash-power all in one place?
Edit: the German news article said the farm used about 5MW, which would only be 10Petahashes/second at most.
I suppose if I want to be unlazy, I can look up how many machines were supposed to be in the facility.
News flash for you!
http://www.datacenterknowledge.com/archives/2014/11/06/knc-miner-to-build-another-20mw-for-bitcoin-mining-in-sweden/Because they can.