I am fairly certain there is nothing 'toxic' in the Packard complex, it really is just a big concrete shell at this point. Regardless, the production company would go about it the same way any other demolition company would, and would probably hire a legitimate demolition contractor to actually carry out the work. Any significantly large production, in this case one in excess of $200 million, would do all proper abatement work, take all necessary safety precautions, issue all resident & neighbor notifications, and be in touch with the city & building owner about the type of demolition, any explosives being used, etc. The Dark Knight famously piggybacked on the demolition of the Domino Sugar factory in Chicago, and the process would have been similar. Blocks were closed in every direction, nearby buildings evacuated, etc. Same for the Hudson's building or any large implosion. But Transformers won't be knocking down the whole Packard Plant. Maybe a section, side, or single building [[even that would be surprising). I think they are really just hoping to set off a lot of 'soft' explosions there and dress the place to make it more 'picture ready'.