Maybe if the fuel line pops off and sprays it's self all over the SC and exhaust manifolds there mabe a fire, but you run that risk with every car.
I have heard this wise tale along time ago, and it is not true.
Not to sound like an ass, but why don't you do a search on clubgp for supercharger fires and see what you come up with. Reason why is because it has been around soo long you can get a good idea of how many times it has come up, and I cant remember hardly any for the 5 years I have been browsing the site.
Good luck