After a lot of research, finally I purchased the New Maruti Wagon R CNG in April 2011 , the vehicle comes with Factory fitted CNG kit, which full fill all the ARAI safety norms and safe for use.
The CNG is fitted in LXI variant so you have to expense little more on Audio Playes, wheel caps etc. Overall the vehile is spacious and comfortable. The CNG cylinder is fitted in the boot of the car so the boot space is compromised so no space in boot.
But if compare boot space with Mileage and Petrol cost, you will proud of with your decision for CNG. I have crossed 500 KM and overall I am satisfied with the car.