You can stitch this in Hugin using advanced features. Basically, the
input image needs to be included in the project four times, each
version needs to have different cropping and d,e lens parameters to
isolate the four bits of the image you need.
I'll attach a Hugin project file that stitches your sample photo - if
the camera is consistent you can use this as a template for stitching
all future panoramas.
--
Bruno