You can set the values of the strings (Text2) to the auto-text names used by PlotMaker (such as <CLIENTNAME>, <DRAWINGNAME>, etc.). This will pick up the value when the drawing is placed in a layout. As I think about it, this is probably what you were looking for (more or less).
There is no (simple) way to read the info back into ArchiCAD.
My intent was to grab one of the settings and have the text on a GDL update depending on the value of the setting. Specifically, my company is registered under a slightly different name in two states. I want the GDL to check the state and display the proper name accordingly.
That may be what I inuited in my first (brief) response. The library parts lose their intelligence when they get to PM and AC has no way to get the info itself. There is a Project Info dialog (look in the file menu) but this doesn't have the fields you are looking for and likewise has no connection to PM. The values aren't available to GDL scripts anyway, as far as I can see.
It seems that you can do what you want pretty simply though by just having different title blocks for each state. The easiest thing is probably to make two company logo/data blocks as PMKs and link the appropriate one to your master sheets.