I would rule the timing to the line that says "The heroes control their ally." within the quest setup (in the quest guide). See if that's before or after "the heroes place their figures on the entrance."
Rule book says:
"The ally’s token must be placed adjacent to a hero at the start of a quest."
Which isn't a specific timing step, so I would go in order with quest setup.
Quest setup order is also why the monsters usually get placed AFTER the heroes get place, unless that rule is also specifically in the core rule book, but we've always played this way due to quest setup rules.
I wish I could reference one of the quest guides but I'm at work. Why can't you ask these questions when I'm home?
Edit: Also putting Trenloe one space closer so he's within 3-movement kill range seems "exploit-y" and I would never do it even if it was in the rules.
Edited by Carbini, 28 August 2014 - 12:12 PM.