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Right, so we know that staying out past the mission timer means the fog attacks, and every time it does someone could die - depending on their guard rating and/or whether they're in someone else's guard radius (and dependent on that person's guard rating).

One would expect though that once someone makes it back to the train that this person is then considered on the train - i.e. no longer subject to being attacked by the fog since they're now inside their comfy powered carriage.

Unfortunately this is currently not the case!

I had four of my guys scavenging and guarding near the entrance to this supermarket - all of whom made it back well before the timer ran out. This was my fourth location on this stop, so the timer was only 1:23 and I had my engine on since my battery was almost dead from the last three missions.

There happened to be a large number of people camped out in the back of this large supermarket, and rather than just leave them, I thought I'd have a go at a rescue. So I used one of the two cops on this mission to go on a guard mission right to where they were - full round trip of over 3 minutes.

I fully expected this guy to die, despite his high guard rating - the fog was >70% and climbing, and most of the location was full of thick fog.

Thing is, this guy made it back in one piece - after more than 2 minutes in that mess! Problem was, three of my other guys - who had supposedly made it back to the train in well under the time and were supposed to be on board by now - got wiped out! The survivor of the group that got back early was another cop with similar guard rating to the lone hero I sent out for two minutes.

Naturally the lazy shits hadn't even bothered loading their haul onto the train, so I lost that, plus I lost their equipment as well.

So, tl;dr:

Currently ALL lottery winners are considered to be "out in the fog" until they every single one of them is accounted for (either reaching the mission end-point or dead).

And they don't appear to bother loading anything onto the train until the end of the mission either - as opposed to when they arrive. But that issue can be fixed by just ensuring the idiots are safe once they reach the mission end-point (barring unpowered carriages and the like).