You alluded to [read below] please do tell us what that "ground reality" is?
The Iranian border fence is about half a mile
[0.5 mile] west of the actual border. On Pakistan side for hundred miles there is nothing but sparesly populated vacuam that has precious little Pakistan government control. The region is essentially lawless 'wild west' and source of problem to Pakistan [smuggling, crime, Baloch insurgents, sectarian terrorists] and frankly Pakistan does not have the resources to stamp state authority. right now the Indian border and Afghan border are priorities. However as CPEC unfolds and Gwadar takes off I suspect Pakistan will need to secure this area and develop roads, police posts etc.
The point that might be valid to this thread although of little consequences to the sick individuals afflicted by sectarian hatred [both sunni or shia] is that Iran could have interdicted the terrorists east of the fence and police compunds as we can see the actual border is well east of the fence.
@Oscar @Dexon @Iranians