Work began shortly after acquiring the HP 4952A on November 10, 2018. The HP Computer Museum has many great resources on these Protocol Analyzers in the 495x series, including the 4952A. There we can get some disk images (unfortunately in TD0 format) with most of the software and examples HP released. The service manual (with schematics) isn't available from anywhere I've found - however the 4951C service manual is available.
With this in hand, some examination of the boards, and dumping of the ROMs we can confirm that there are significant similarities between the models. Eventually I would love to have full low-level documentation on the IO & Memory maps.
At this point I have deciphered the menu data formats, the runtime linker used in HP's applications, and how to do some basic text output.