Here's some background: The insurgency in Pakistan isn't one modeled on Mao's method (against which US counter-insurgency doctrine is based). In those 20th Century insurgencies, the effort was run as a replacement for the nation-state, replete with ideological purity, hierarchical leadership, and wings for government functions. In modern, 21st Century insurgency, the groups that participate are self run (autonomous) and built from different (usually local) motivations/loyalties. What leads them to work together is a common dream, a plausible promise of what might be. Pakistan's open source insurgency was sparked into existence by the Red Mosque siege and has now found a plausible promise -- economic and social justice through land distribution and sharia courts. Rapid growth is sure to follow.
Some more reading:The alliance is based on more than shared ideology. “These are tactical alliances,” said a senior American counterterrorism official, who spoke on condition of anonymity because he was not authorized to discuss intelligence matters. The Pashtun Taliban and Arab militants, who are part of Al Qaeda, have money, sanctuary, training sites and suicide bombers. The Punjabi militants can provide logistical help in Punjabi cities, like Lahore, including handling bombers and target reconnaissance... One such joint operation, an American security official said, was the Marriott bombing in Islamabad in September, which killed more than 50 people.