The solution some 20 years ago, when the local council acquired the area following Haig's closure, would have been to create a relief gully north of the moving mass and allow the sea to clear material as it moved down there.
Instead they "landscaped" the whole area, placing a great heap of pit waste on the weakest area of cliffs (400m north of Saltom) and wondered why it collapsed. At Saltom they decreed that the sea was eroding the cliff base, allowing "the tipped spoil from Haig Pit" to encroach onto the site. The weight of pit waste from Haig was also blamed for the whole collapse of the cliffs along here but they were eroding long before any tipping took place.
They also stated that the sea wall at Saltom was being "eroded by the action of the sea" but this is utter ****. The wall, north of the shaft, was pushed outwards by the mass of flowing sandstone from above - initially a few blocks rode over the wall onto the beach in the 70s before the increasing mass caused the collapse. Gabions were emplaced by the NCB at this place at that time to prevent the sea flushing the backfill around the shaft (then still open and connected to Haig).
The landslippage seems to be associated with the Ravenhill Fault which runs east-west, downthrow north, through here. The fault brings coal measures on the upthrow side against Whitehaven Sandstone to the north. The softer mudstones to the south had long since eroded leaving a number of large sandstone blocks (some 2-300 tons) perched on the slope above. Within the Whitehaven Sandstone are shale beds which erode more quickly and are also more impervious than the sandstone. With a seaward dip this produces a conveyor belt effect of blocks moving forward on the sandstone/shale interface and then toppling. As it is happening at some 100 ft or more above high water mark and in places above where no cliff base erosion occurs (protected by outcrops on beach) it seems that the sea is an unlikely cause.
So, to answer the question - yes, they'll just let it slide. And perhaps if some fissures open up in the top they will doze some more material from above down to fill them up and destroy the engine house a bit faster.