I would agree in general but I see a big potential loophole. What about foreign sim cards? Does Pakistan plan to apply the same restrictions to people who visit the country? If so then I would think that this might provide a significant hindrance to international tourism and trade - "no cell phone for you unless you go register it with the government while you're here!" On the other hand, if they don't do it, then lawbreakers will just get foreign sim cards.
Maybe the government could make a fairly painless process for foreign visitors.. for example, sim card registration at the point of entry to the country, for those willing to do it (and for those not willing to, they just can't use their phone).
I thought about other potential loopholes, such as phone / sim card theft, but one presumes those cards would be rapidly disabled when reported. A rather nasty possible workaround to the problem would be to kidnap and murder people, steal their phones, and continue making payments in the deceased's name until someone catches on. That could of course carry a risk that if someone did catch on, instead of disabling the stolen phone they may just use it as a beacon to catch you. Satellite phones would work, of course, but they're a lot more expensive, both in terms of hardware and service. And someone not associated with the government in Pakistan using a sat phone is probably as it stands immediately be flagged on the watch list of anti-terrorism task forces the world over.