This is a bit of a wild guess but could you add something like this after the script (ie on a new line after the final "]."):
self controller: !Progress setTo: 1 atTime: (line * 500) ms.
I'm wondering if that would give you a !Progress fader that would become 1 when the scripted events have finished (or to be precise 500ms after the final event has slid to its value).
I had a chance to try this out now. Any controller I put in the script isn't visible in the VCS. But if I put a SoundToGlobalController to the left of the script I can display that controller. So for the example above create an STGC with these parameters:
!VisibleProgress should turn up on the VCS and show the value of !Progress.