Well I went over to the Lansdale Historical Society today. They have county maps (including the original that I linked to in my first post) that show a turntable in the yard. The Sanborn maps from the early 20th century show no turntable at all. I'm guessing the one shown about was ripped out sometime between 1895 and 1914.
Interestingly enough, they have an aerial photo from 1951 that shows what looks very much like a turntable pit beyond the wye where what is now left field of the softball field. That photo also shows hundreds of ties stacked up all over the place in the yard and where the ball field is now. In 1955 they were gone, so I'm assuming some kind of huge track replacment project was going on at that time.
I asked if I could photograph the picture (it's huge, must be 3x4'), but they have to check into that for me. I also asked them to look for any old track diagrams for the yard. When they get back to me, I'll report it here.