@Poster, Probably thats showrooms particular warranty. I doubt that they are permitted by Indus Motors.
Are you sure Santros CNG model was 72k ? I remeber in 2006 Santro Club was 559,000 and Santro Club GV was 609,000 While Culltus VXR CNG for 599,000 (yes cultus was cheaper being a non CNG car)
Plus Santros boot was also redesigned so it could fit cylinders with out taking any space, and the spare tire was kept up.