Thanks Mal and Wayne! You've confirmed much of my suspicions.
Wayne, similarly I thought from memory the About Dialog would yield some clues (I'm sure you've showed me that before), I guess it was just that the 32 bit version doesn't tell you in About, only the 64 bit.
Mal, there is the logical way I thought it would have been done, and then there is the way our contractor system architects decided to deploy software in Win 7, despite my warnings! As you've alluded to, because there are different potential combos with ArcGIS, AutoCAD and Office on the PC (requiring different Bentley installation and CAD/GIS integration scripts), I would think it very hard to create a "standard" network installation package for the products. The simplest way I would have thought was just to let Bentley's own installer smarts figure out the right combo and do eg. prerequisite checks directly on the PC, but of course our ICT gurus have chosen the hard path of effectively creating their own installation packages and scripts! (based on SS3 to boot, so we've been downgraded).
Our ICT environment has deployed WaterCAD/Gems/Hammer to program folders like this:
C:\Users\067944\AppData\Local\Microsoft\AppV\Client\Integration\CEF9BBB1-02CD-4722-ADA0-5CAF5B5700D5\Root\VFS\ProgramFilesX86\Bentley\WaterGEMS
I suspect this is a key reason we are having almost 100% runtime errors/model open/run failures with eg. Runtime errors for trying to find non-existent program folders/files:
"System.IO.DirectoryNotFoundException: Could not find a part of the path 'C:\ProgramData\Bentley\WaterGEMS\8\PredefinedWorkspaces.xml'."