Just to add, in Islamabad you CAN GET temporary number from ETO. I had a City which had IDF series number. The SAME number was issued to another car. As we were waiting for a series to start and we wanted a special number, we kept that IDF number. After some time, we got IDS series number.
My friend bought a car and it was unregistered. He used that car with the number of another car that he owned. So, there were two cars with the same number in his home. That was illegal, but his car was totally genuine.
I had a fake number on my Corolla before it got registered. The number was of Gujranwala and had all "2" digits. Why I did that? That car used to make multiple trips from Islamabad to Gujranwala and Sialkot. Police stops and creates issues for you when you have "Applied For" written instead of registration number. The car was and is legal but the plates were fake/of another vehicle that we owned.
I can give more examples. The point is, temporary or fake numbers can not assure you that the car is NCP. ETO does provide you temporary numbers. People do it because it could be done easily in Pakistan and they can save themselves from the Police. But yes, if they get caught with fake number plates, they can be in deep trouble but people take the risk in Pakistan as more chances are that you'll not get caught.