Well...
I know that all of the soundstages were a part of Backstage pass, because there's a tour lane that runs through all of them. Originally, backstage pass was a part of The Backlot tour, which used to last roughly 2 hours...in the days when the studios were more utilized for actual production there would be things going on in the soundstages all the time, and hence fodder for the tour. I believe that a few of them housed different things over the years, such as the honey I shrunk the kids bee/blue screen demonstration, and the bette midler "lottery" film and subsequent "sets" (the idea being you watch the film, and then see the sets on the soundstage, like they JUST finished filming it...pretty neat, if I remember). I don't know the details, but apparently the trams loaded at the end of this walking tour over @ the Animation tour building. There's a long over hang of roof, making a covered area - this is where the original queue for the trams used to be located (you boarded them after the walking tour/backstage pass). Interesting note: It's still show-acceptable for Disney/MGM Studios CMs to wear the old backstage pass long sleeve jackets in cold weather (at least it was last winter, at movie ride) - it's interesting to see them walking around with history on their jackets...
The problem with the whole backlot area is that since it's cut off by the highway, there's no room for expansion, which is why part of the backlot was demolish for LMA. I love LMA, but I wish there was a better place they could have put it, or maybe just a way they could have reorganized the backlot...
- Brian