Stairs were built (I think) almost 40 years ago, when the rear part of the Pop Side was levelled to create the training area (which itself became the present-day outdoor concourse). They may have been an emergency exit, and I have used them once myself to leave the ground... but that was years ago! They lead onto a fairly narrow path which took me up to the roundabout at the end of Castle Street, IIRC. No idea if they are still in use though?
BUT...you can see in the image that there is a substantial area of banking at the rear of the terrace which has ended up outside the current concrete fence, and I believe that this land may rightfully belong to the club.
The proposed block of flats would go where there is a big mess of trees and rubbish, in the angle formed by the edge of the bowling green and the emergency steps.