Finally got back to this...
NOTHING we have tried seems to fix this.
The EA.App value seems to require: C:\Program Files (x86)\Sparx Systems\EA_909\EA_909.exe to be active (notwithstanding the entry to Interop.EA.dll)
We want to test our Excel automation against: C:\Program Files (x86)\Sparx Systems\EA_Beta\EA_Beta.exe
We replaced as many occurrences of EA_909 with EA_Beta in the registry as we could, we rebooted immediately, and confirmed all the obvious instances had been changed. (Our registry editor won't fix REG_BINARY entries, but from the looks of them, they shouldn't be the problem).
Nothing seems to work, it always goes back to: C:\Program Files (x86)\Sparx Systems\EA_909\EA_909.exe If that exe file is NOT open, then the automation (via the GetObject) will not see the App. Even though we replaced the EA_909

with the EA_Beta one in the EA_909 folder.
So, in the end,
in desperation, we copied the EA_Beta folder into the EA_909 and renamed the executable and opened that! EA.App now see the v13 EA (in the guise of EA_909.exe).
Can anybody, especially a Sparxian, tell me what's going on?
I don't have any hair left to tear out, but I tried...
TIA,
Paolo