It's not clear to me if monsters/enemies can attempt to escape from combat.

The "Craven" ability says they will try to do so when their leader is slain.

Is this the same as how players would do it?
i.e. after a round of close combat they can attempt an Athletics (Movement) roll TN 10+Body of players engaged?

If the monster/enemy is only engaged in ranged fighting is it different?

If the players are willing to let them go, then they will just flee. Otherwise, I'd use the same mechanic as player characters attempting to escape, yes.

Agreed. The only reason the Runner should need to roll the dice is if their is some opposing action by an Opposer. No action, no Opposer. Without an Opposer the Runner escapes successfully.

Note that the terms Runner and Opposer are used instead of character or adversary/enemy because it makes no difference which one is in which position.

Of course, for story purposes the Loremaster may just let things happens due to campaign or narrative need.

This.

Unless there's a good reason (e.g. "You have to stop the lookouts from raising the alarm"), I would tend to narrate it so that it's clear there is no reason to track down every last orc.