Is this first time the car has ever been missfuelled?
Was the car running ok prior to this missfuel?
And are you sure the dealership didnt start the car once it was left with them?
Its seems rather strange how all that damage could occur buy filling up with petrol by mistake..and not even start the engine up... What should of been done here onthe outset was to drain the fuel tank out onsite..theres lots specialised companies who can do that and if not BMW should of done once the car was in their pocession...then refill the tank half way with diesel this means that any tiny amount of petrol/residue that may still within the tank will get diluted..and shouldnt have any adverse effect on the engine.....Of course metal filings can be a sign that wear has occured on one of the pumps either within the tank or the high pressure on the engine over a period of time of running..but of course if they should also inspect the fuel filter as thats normally the first thing to check or even replace during a missfuel....I doubt the computer would in all honesty..but you should enquire/investigate if the car was started coming off the recovery vehicle or in to the workshop..that may of coused that.. I genuinely cant see how all that damage could of occurred if the car was never started when it was loaded on to the truck..it would take a short while of running on the wong fuel to cause that amount of damage/cost...A second opinion could be to way forward..