Hi The Fighting Hellfish;
Sorry to welcome you to the forum in this manner.
If the butts where touching the back wall, then most likely that could have caused the fire. Another possibility; especially when you have a lot of fatty cuts like butts, the drip pan can get clogged (using a sugar based rub also contributes to this problem). This can cause a build up of grease on top of the drip pan; being that close to the heating element - that can ignite the grease. One other factor is not changing the water bowl. The bowl will fill with grease; displacing the water - and if you sill have the burnt bisquettes in the bowl, that could ignite.
The best way to proceed is to access the damage before contacting Bradley; and work with them to see if your Bradley can be fixed, or need replacement. Check inside the cabinet to see if any of the walls are warped. If you have the time remove the back cover, you can check to see if the insulation has been melted, and/or if there is any fire damage to the wiring. If you have a multitool, you can test if the inline fuse, and sensor are still good, but checking the continuity. If your temperature sensor and/or inline fuse haven't been damaged you should be able to test your generator. Though most likely your generator is alright. It sounds like you caught to fire before it could cause damage to the generator.
Good Luck. Let us know how things work out for you.