As there is no requirement to enable re-entry from the escape stair, this sort of issue tends to emphasise the need to prevent doors to lobbies and stairways from being wedged open eg for convenience or aditional ventilation), keeping stairways free of combustibles and the value of knowing where the fire is (eg addressable alarm systems). It seems to me that, in this particular case there is a need to consider within the risk assessment whether there is a significant risk of fire/smoke (or indeed other hazard) within the stairway and, if so, what are the control measures - which could include additional lobbies, door alarms, further instructions to staff, etc. That said, it can be useful in normal circumstances to be able to get back into the main building from the stairway when the door closes behind you. I've found the same sort of problem with store rooms, electrical intake rooms, boiler rooms, cellars, etc in new buildings where they have designed for a handle on one side of the door only or for key only operation and a self-closer.