When my group ran this mission the other night, I ran into a bit of confusion. Unless I skipped the part where it said it, I don't believe the campaign guide stated where the escape is. We ended up using the Rebel deployment point as the escape. Furthermore, how does on escape in general, if not stated? Would one simply get to the escape or would you have to get to it and then be able to move again?

You escape by spending a movement point while on or adjacent to a space specified in the mission (RRG, p. 12, under "Escaping). I can't remember that mission specifically, so I don't know where is specified, but I know at least one mission I've run required them to escape via the Rebel deployment point.

A simple task says:

A hero carrying the formula can escape through the entrance.

Entrance is defined in the RRG as:

The spance containing the entrance token.

In the mission briefing for A Simple Task (which your imperial player should have read to you) it states:

• A hero carrying the formula can escape through the entrance.

"Escaping", RRG, Page 12:

Certain mission rules can allow a figure to escape. In order to escape, the figure must spend one movement point while in or adjacent to the space indicated in the mission’s rules.

"Entrance", RRG, Page 12:

Entrance refers to the space containing the entrance token. Heroes are deployed to the entrance token at the start of a mission in a campaign.