There are things happening in the game world while the Player Character does his work.
Are those outside events triggered by certain actions (like entering/leaving a scene, or progress in story), or more of "real time"?
Thank you!

Technically it can be both.
All actors (NPCs) have their own schedules and are continuously updated / checked for changes on what they should be doing or where they might be strolling or standing around etc.

But certain actions for McCoy (or other actors) like exiting or entering a scene could trigger a behavior change for other actors as well.

So, McCoy can be standing around in one scene, and actors will be going about their schedules and finding out about stuff, changing their locations, exchanging clues etc in the background and a few may even enter the scene where McCoy is waiting. Or if they are running away from McCoy, then if it takes too long to follow them, they will be gone...

But in other occasions, leaving a scene or entering a scene or starting a new Act, etc, will introduce more deterministic behavior change (like them appearing in the scene that McCoy just entered).

I wouldn't worry about that much.
The game actually expects the player to take their time and explore for clues for their investigation.
It's only a few occasions where you could hurry (but for a few of those you can choose not to) and it's very obvious why (probably because you're supposed to be chasing a fleeing suspect).

It is also not possible to reach a dead end state if you don't hurry or spend a lot of time in a location or even if you missed lots of clues somewhere and can't find them there anymore. There should be always some alternate path to make the story progress.

Thanks again, that's relieving!