Typically, the game goes as follows: new laws get drafted, local groups such as auto rickshaw unions get together and demand time/cash incentives to move to more expensive, cleaner equipment, local governments grant extensions, and the cycle repeats.
Then there are the general issues plaguing enforcement in India, which are listed in the wikipedia article.
A majority of drivers in India never took a test - they simply bribed an official to receive a license. Only a fool would pay the Rs 20,000 fee for a commercial vehicle roadworthiness test when the certificate can simply be bought for Rs 1,500. It's easier and cheaper to pay bribes than to work through the official bureaucracy.
http://faculty.chicagobooth.edu/marianne.bertrand/research/p... http://siteresources.worldbank.org/PAKISTANEXTN/Resources/Ur... http://thewire.in/16474/why-swacch-bharat-type-schemes-will-...
While I agree on the point of vehicles made pre norms, but vehicle manufactured after their adoption are all mostly going to be compliant (although with the VW scam, I'm sure there are going to be significant doubts about whether the vehicles stay that way).
Can't argue on the emission check though, that I definitely believe. One can only hope newer vehicles don't have significant degradation in emissions over time.
I guess the main takeaway is that the Indian government has to enforce the rules more than anything.