If you note your own article, it was dated 2012. If cancellation of spectrum was a reason for the hike, the hike would have happened at least 2 years ago. Most operators already held spectrum from the bidding in 1994 (whose lease recently lapsed) and later in the early 2000s (its a 20 year lease). The thing about the 2G scam was that all the spectrum was restricted to only 2G technology, which meant that 3G and LTE were not allowed on it. The new Feb 2015 spectrum is free for use on any technology. And you are right, the telcos would have a full financial model and valuation in place to analyse their expected revenues based on the rates they charge customers and their investment in spectrum and their capex. Here's a link to the Department of Telecom bidding document: http://www.dot.gov.in/sites/default/files/NIA_Spectrum_Auction_January_2014.pdf
As an example, for Delhi for 900 MHz, its Rs. 360 crore per block. To run 3G or LTE, the company needs to buy at least 5 blocks of 1 MHz each i.e. Rs. 1800 crore just to run 1 band of 5 MHz 3G or 4G. On top of that, since its an auction, the price it will finally sell at will be higher, may be double or triple the amount, as 900 MHz is highly coveted. The only way to sustain and hold the market is to buy the spectrum and raise call rates to sustain, as they will have a minimum expected ROI from their investment. For a circle like Delhi, as there are only 16 blocks, only 3 operators can successfully run 5 MHz out of this bidding. So its more like Game Theory where out of the approximate 10 operators, only about 4 will sustain on 900 MHz in 3G or LTE in Delhi. They would be willing to pay just about anything for it if they have captured the market and based on their calculated market size, expecting a higher pay per customer makes it more sustainable.
My point here is, they have a strategy in mind if they are raising prices to sustain and maintain their ROI. Just about all operators are raising their prices to cover cost of the new spectrum. If an operator didn't, mostly he may not have purchased spectrum in that circle and don't be surprised by getting more frequent call drops. India has one of the fastest growing telecom markets today, so the telcos aren't even worried if some customers leave, because they can now provide new and better services with the new spectrum.
As another example, when Tata Docomo launched in Delhi, they offered unlimited internet at very cheap rates compared to other operators. Many people signed up! Since they charged less and couldn't invest much in network equipment, customers suffered bad connectivity and they only spoiled their brand reputation.
Nobody's denying producer equilibrium, but telcos have a better vision of the market to know when they can raise prices and still sustain.