Our solution took quite a bit of R&D effort to set up. We wrote our own web service for invoking CALLAPI and run it on an in-house web server. This has been a very handy tool that allows all of our applications to directly launch UC4 processes. However CALLAPI can be a wide open backdoor into your systems, so we designed our web service to only accept the name of an object to launch, a parameter list, and the name of the object to launch must match a white list entry. I can share its behaviors, but I don't think I can share its source code. I don't even know where it is!
For a less expensive solution, could Sailpoint write a trigger file? Or could your UC4 process run once an hour and check for workload?