I will play the devil's advocate here and view things from Pakistan's perspective.
The GB area is extremely important. It gives them a direct land route to China and prevent Indian access to Central Asia.
Plus it is has the approach to Kargil and hence Ladakh. This also makes it useful for making Siachen untenable for India.
Containing a conventional Indian thrust into GB has low chance of success - considering the terrain and logistical difficulties. A determined enemy can seriously impede Indian advance by simply blowing up the approaches to Skardu.
But honestly speaking - Pakistan's posturing here has largely been defensive in nature. The infrastructure is still dismal and might I say, of 1950s time(almost)!
@Joe Shearer can help wrt to this tactical situation.
those days are not far when every person who is not a Deobandi terrorist will have to keep weapons for himself
In any war of the future, the period of conflict will most likely be restricted to a few days. In such short notice a region as vast as GB cannot be taken back - especially considering the fact that the place is defensible and also the individual training and motivation of the Pakistani soldier( in this case that will be the GB scouts, yes I don't underestimate them)
Pre war 'Brandenburger' actions, fifth columnists, behind the lines and paradrops are the only way to quickly clear the area. Even then it is very very difficult, simply because of the advanced radars that are surely there to spot any untoward movement of aircraft, thus making paras very very risky or even suicidal.
