Reasons Behind Airtel's Choice of Kolkata as 4G Launchpad

Yesterday Airtel rolled out country's first 4G services in Kolkata. And many are wondered why Airtel chose Kolkata as 4G launch pad! The Telegraph India frontpage of 11th April said: Mystery of Calcutta turning 4G launchpad - All you wanted to know about the faster telecom service plus the debut theories. 

Airtel created a landmark in the history of wireless broadband in India, as Airtel 4G LTE, country's 1st 4G services launched in Kolkata on April 10, 2012. Details of Airtel 4G plans, devices and VAS are available here. (BSNL WiMAX was launched earlier, but no 2Mbps+ plans means you never see true potential of 4G.)

Before you say OMAAGAAD ! let me explain. I will also mention Telegraph India's points.
I asked our sources close to Telecomtalk that despite of the fact Kolkata is the lowest ARPU generating metro circle why Airtel chose it as country' first 4G city. They explained like these:

1. Broadband penetration is low in Kolkata, so they can capture untapped data market with 4G (broadband revolution). That leads me to think that pricing could be affordable and user-friendly. But ultimately Airtel brought plans targetting mid-user or enterprise customers, while device cost will keep most people at bay!