No, you cannot access the trimmer via scripts but since the trimmer is no different than the timeline I don't see why you need to. The trimmer is really a scratch pad for doing things before you put them on the timeline. With a script you can always create a temporary track as a scratch pad to do things and then move events onto the other tracks and delete the temporary one (using it like a trimmer).
What is it you want to do with the trimmer that you don't feel you can do with a script?
Because the trimmer area is a scratch pad, I want to be able to do my manipulations in that area and then create subclips directly. Just like everything I put into the trimmer won't be included in the project, I want to be able to run my manipulation scripts in the trimmer and only retain the end result. So basically, I'm running a script on a clip rather than the whole of the project which to me would seem useful.
A good example is my Regions to Subclips script. I define alot of my regions in a clip up front in the trimmer and at the end, I'd just like to automate the subclip process right then and there. What I'm forced to do in my current script is to define ALL regions then run my script when I'm done which works but the other way would be ideal.
I consider the main timeline my "working copy" which is where everything I want to include goes but I can see alot of use in being able to run scripts on the trimmer. I hope they add it someday.