Shafiq, any engine is capable of being run on CNG including any forms of transmissions as long as someone knows what they are doing. I was looking to buy a Lancer myself a little while ago. I have an acquaintance who imports Lancers only and he gets CNG installed for customers. As far as I know, no one has complained regarding CNG and a blown up transmission. If you don't experience a sizable lag in pressing the accelerator and finding power at the wheels, your installation is working fine enough.
With all due respect Naveed, CVTs do not have any gears. There are typically two conical pulleys that are shifted through hydraulics in order to vary the length of the transmission belt. When someone installs a CNG kit on a CVT, they fail to account for engine tuning differences. Gasoline has a higher calorific value compared to CNG. Essentially a CVT on CNG would experience large kick in delays which means lower acceleration. If your CNG installation guy is competent enough, he will install a lembda to deal with the delays and will tune your system accordingly.
Moreover, "forces required to shift gear" are not necessarily produced on low RPMs. I could demonstrate shifting "gears" in any automatic transmission above 3,000 RPM all the way to 6,500 RPM.
As for heating up automatic transmissions, frequent shifting tends to wear out the bronze discs that act as clutches in automatic transmissions. When you hear someone tell you, CNG blew up my transmission, it typically means that sensors were improperly integrated (at times even bypassed by shorting) and a tuning was not performed. These issues mean that your ECU is increasing flow rates (both air and fuel) in order to come to the required torque and RPM levels in order to perform shifts but as soon as the shift is performed, the engine underpowers and moves in for a lower transmission ratio. The frequent shifting tends to heat up the transmission oil which is typically synthetic. As soon as the oil wears down, you have organic acid and carbon residue formation which act as abrasives for the bronze discs. If you happen to pull out an automatic transmission that "burned up" you'll find soot practically sintered into the bronze discs. Once the discs wear down, there is no solution except for replacing the entire transmission since no one in this country seems to repair them.