You misunderstand. PIA would pay for it out of its own budget. It would be a cheap airline option. It would help both PAF and PIA due to economies of scale, and given that depo level maintenance is now possible at Kamra.
Meaning low cost and a win-win for everyone. People in Europe may not prefer the Saab-2000 because of the somewhat higher level of noise, and slightly slower speed, but people in Pakistan don't care about such things - they care about the cheap price of the ticket more. Assuming my presumptions are correct, which actually could be wrong given that I know next to nothing about running an airlines.