I am having a similar issue with 1.1, I answer a callout, and arrive on scene, sometimes the NPC's are there, sometimes not. If they are there they are marked as red blips, as normal, but nothing else happens, they don't do anything, just behave like normal NPC's would, and nothing will resolve the callout, they yellow circle stays around the area, no matter what happens.
This happens with all callouts, I have looked through the diagnostic tool's logs and It says something like:
[Warning - 8:42:43 PM] [script.Calloutmanager] EndCurrentCallout: No Callout Running
I'm assuming that the callout failed to load it's scenario data or something like that, don't quote me on this though.
if anyone can help me with this issue, please post a solution.