OK, managed to solve the problem for me.
Turns out the above warning in the log created by Sierra is a red herring. I see the exact same set of complaints from the same application on the machine where everything is working fine. In deperation I went to the place I really should have looked in the first place /var/log/system.log. (Ill flog myself on my own time) Lo and behold:
Sprint SmartView[502]: SERIOUS WARNING : SERIOUS WARNING : RW permissions bad on directory '/Library/Application Support/Sprint SmartView'
Sprint SmartView[502]: SERIOUS WARNING : Aborting (Installer was not run or shared folder missing attributes)... (20)
So I asks myself, I asks, "what is different here?" I have a look at the permissions on '/Library/Application Support/Sprint SmartView' on the busticated machine using ls -al:
drwxr-xr-x 4 root admin 136 Dec 15 13:40 Sprint SmartView
I look at the same permissions on the happy machine:
drwxrwxrwx 8 root admin 272 Dec 16 07:57 Sprint SmartView
Well wadaya know?
So lets fiddle with the perms and let anyone do whatever the heck they want to in there.
sudo chmod 777 '/Library/Application Support/Sprint SmartView'
drwxrwxrwx 8 root admin 272 Dec 16 08:15 Sprint SmartView
Bing! Everything works just fine for me. I post this updated from the formerly busted machine via Sprints much vaunted 4G network.
WILD GUESS WARNING: Maybe the permissions on the '/Library/Application Support/Sprint SmartView' get bunged up durring the migration and the installer is too brain-dead to detect it?
Hope that helps the rest of you.