I'm going to get right to the point. My band played a show last night with our friends in another band. They went on first played 3 songs then the bass players amp went out. After messing with it for a few minutes and still not getting it to work i offered if they wanted to use mine being that his didn't seem like it was going to work. Once they plugged my SVT-3 Pro in it started pouring smoke and was sparking. We tried it 2 times. I was wondering if anyone know what could possibly have happened to it or if they've seen anything like this before. I have a warranty from GC and was also wondering what all do those cover? I bought the 90 dollar extended warranty and was wondering if it covered tubes, my friend believes the other bass player's bass (a beautiful Ric) fried both of our amps, and possibly my preamp tubes?
Highly unlikely. It's probably a problem with the power supply which caused his amp to fry in the first place
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It was almost certainly bad wiring at the venue you were playing. There's no way in hell an instrument is going to break an amp unless you mash it repeatedly into the chassis.

The GC warranty probably doesn't cover tubes. If it does, it's probably for the first 30 days. That's irrelevant though, since this is a bigger problem than tubes. Tubes do not cause spark or flame outside the amp. The amp needs to go to a tech, and you need to buy a power conditioner so this doesn't happen again.