Thread that fires event signal runs just after the last event handler?

[Bachatronic]

From the Deferred Lua Event Handling:

@WallsAreForClimbing

Right now, all event handlers get called immediately when an event fires. For every instance added to your game, property that changes, or some other trigger that is invoked we need to run Lua code right then and there.

My question is: after the last event handler for that signal is called, the next thread is necessarily the one that fired the signal or could be any other thread?