Yep. That's supposedly for them to ditch in the event that the main engines fail but the shuttle is controllable - they don't have enough energy for a trans-atlantic abort, so they glide and bail out over the ocean.
How far did this plan go? Just because it was discussed and documented and thought through does not mean it was something that was actually going to happen. Was this actually developed and the parts&pieces put into place with procedures written up in the flight manual?
Harebrained is right.