The Government Decision Reversed Later on:

government of Pakistan inverted its former verdict to restrict the popular
BlackBerry services. Pakistani representatives called on and questioned mobile
phone operators to discontinue BlackBerry services to foreign missions together
with apprehension about the security of the communications, industry sources
reported on 31 January 2011. 

blackberry mobile

The Verdict was reversed:

However, later on, the instruction was reversed. Now the officials have again asked the operators to continue providing BlackBerry services to the foreign missions. A representative at the Pakistan Telecommunication Authority (PTA) confirmed that the services continued, further, he stated that The Blackberry services are on for the foreign missions. However, It was not instantly clear why the government of Pakistan retracted the previous pronouncement to restrict the services of the blackberry mobile phone in the country.