For anyone interested - I found the answer.
It appears that when an EPDM client accesses the EPDM system and performs a transition, the client makes certain API calls that require it to launch a task.
So it is not a purely SQL operation as I though originally
Because the required libraries are not installed with the activeX control on the webclient, it is not possible to make these calls, which essentially makes it impossible for a webclient to activate a transition that fires a task addin.
This makes sense because exposing this functionality to a webclient could have negative side effects for skilled hackers.