the whole thread is depicting one side of the story. The only benefit getting Islamabad number plates to the OP/thread poster will be that he can pay his tokens yearly in Islamabad rather than going to Jehlum.
Don't ever think that it will get Islamabad number and then Islamabad number's resale value...hahaha.
Your Original File of the car will get a "transferred" tag on it and when somebody will ask paper at the time of sale of the car, he is gonna come to know the whole story that the car is originally from some other city and registered to Islamabad. So, it might downgrade the thing, but will not upgrade in any case or be equivalent to an originally Islamabad Taxation Office registered vehicle.
This information is handy to those who are willing to transfer to Islamabad number just for resale or some shashka chakkar 