Originally Posted by JARblue

I just tested this. First, the round button at the hatch is the locking mechanism and locks the hatch and both doors. The rectangular button (it is longer, too, like Ken mentions) opens the hatch. This button opens the hatch if the car is completely unlocked or if it's locked and you have the fob with you.

In the first test, I unlocked the car with the fob unlock button (pushed twice to unlock everything) and left the fob in my office. The hatch opened without a problem. At this point I don't have my fob, and when I used the door power lock button, it locks both doors and the hatch. Pressing the power unlock button on the door subsequently unlocks both doors and the hatch.

I don't believe the battery status of the fob would affect the function of the hatch other than you being able to open it when the car is locked. If the car is completely unlocked (not just one door), the hatch should open without needing the fob.

Of course, you can always follow Mr. Ken's suggestion and crawl between the seats if you really need back there