Yes LPG is available in spark as of 5/6/2009.
All auto manufacturers provide mileages under test conditions, which is unnaturally higher than actual road conditions. Spark Petrol users get 16kmpl (highway) 12.5(city).
Chevrolet has not provided mileage for Spark LPG. But it is a known fact that LPG gives 2.5 to 3 kmpl LESS than petrol for any car! moreover LPG is costlier to run than Diesel or CNG.So Spark LPG should give 13.5kmpl (highway). Chevrolet may quote higher milage later on.Remember it would be under test conditions.LPG reduces boot space & has 5% loss in BHP/Torque/Power. But has much cleaner emissions (less pollution) and is cost effective only if you drive at least 50km daily.Cost of LPG is 36 to 38 Rs/Lt. LPG filling stations are quite few as compared to petrol bunks and not readily available on highways. But all LPG vehicles are Dual - they can run on either LPG OR Petrol! check http://www.sumanauto.com/Conversion%20Calculator.asp#calcu