We have access to pdf documents containing the law that completely describe the border of provinces, districts, etc. Page is in Spanish, as are Panamanian laws. Panama/Proyectos/División Administrativa.
The International Space Station has taken images of the Panama Canal and surrounding cities several times over the last few years. Each time the area is imaged there are about 10-20 images taken that can be stitched together to make a layer of the whole area at that particular instant. I have begun rectifying some of these images from the December 2009 pass over the area. The images are not quite as good as the Bing highres images, but they cover areas that are cloudy in the Bing images and are good enough to trace rough building footprints from. The imagery layer (see it online here) can be activated in JOSM with the following WMS link: