In response to the question on BACT/LAER. BACT is indeed a top down approach, and the end user can consider just about any economic/environmental aspect for assessment of project feasibility. For example, if an emission control device might not fit (physically) because of plant layout, it could be excluded.
LAER, on the other, doesn't care how much it costs. If you need a platinum coated catalyst 60x40x50 feet, you may have to install it even if the expense is inordinate.
One aspect of BACT and LAER (and BAT) that I find appalling is that the actual concentration of exhausted pollutants could be less than the pollutants inducted into the facility, but you don't get to count that towards the project evaluation. A major hole in the process evaluation, I think.