They can leave hyperspace at any time, but only with a functional jumppoint generator. Small craft like Starfuries and civilian freighters usually wouldn't have these, since they are expensive and require a lot of power. Warships and explorer ships often do have them, especially the larger ones. However, the explorer ship's drive was damaged in this episode. Note that even if you can leave hyperspace whenever you want, you still need the lock-on signals to navigate. Otherwise, you could come out pretty much anywhere.