Think of it this way. Line speed is thickness of the broadband pipes. Speed is still controlled by the software. If the line is not thick enough, the water would flow at a slow speed even if there is enough water available to flow through. Line speed should be more than the package speed as there is some speed loss as the distance from the exchange increase. Internet speed is managed by BSNL servers.
In my case, the line speed was set at 4000kbps on 4mbps plan. I would never have gotten 4mbps because 4000 < 4096. Plus because of the distance, the actual speeds I got was around 3.0-3.2. Once they increased the line speed to 6000kbps, speeds increased to 3.5-3.6mbps. Sometimes more if the congestion on the network was less.
The problem with line speed is that line quality goes down as the speed is increased. So ISPs tend to keep it low if the last mile wiring is of poor connectivity. There are a lot of factors involved. As long as the SNR etc. values are extremely good, increase in line speed by 2mbps should not hurt.