Sorry to hear that. I don't recall having to remove the fuel pressure and return lines engine side when replacing the autotransaxle or doing repair work on it but sometimes it is better to do that since there will be alot of engine movement while using an engine hoist to hold the engine from above. The subframe that holds the engine and transmission must be removed and then tranny dropped down. Fuel line retention points should be removed like any clamps or brackets since it will be moving and flexing. Hard to say the shop is negligent and maybe hard to prove but the fire did occur after their work so a presumption is there.