Couple of Meters across ? . Mortar is a part of small ranged artillery which can be placed back and adjusted and then fired on the fence. There's already shortage of fence on LoC , and definitely we don't need to destroy normal fence , but smart fence could be a problem .
Pakistani Intel. must know . Most probably Iran is going to help them to take AJK from Pakistan . I could be wrong but given the highlights of activities on LoC and all , it's most probable that they are taking neighbours into confidence for the upcoming events in South Asia .