I think it would be more accurate to say that only properties in the cities and larger towns do have mains gas.
The optical pulse sensor is unlikely to be useful for either a gas meter or a water meter, as these tend not to have an energy supply and hence do not have LEDs that can be detected. Usually, if any provision is made, it will be either a volt-free pair of (mechanical) contacts or (I think more usually) a moving magnet that is intended to operate a reed switch; or a reflective patch on a register wheel.
Reed switches are notoriously prone to contact bounce. Something that might be helpful - for both gas and water meters - would be a module incorporating the MAX 6816 or a similar switch debouncing i.c. that could be attached to the digital input or interrupt input of the sensor node.
Using a reflective patch implies a light source, which in turn implies a certain amount of power, which tends to preclude its use with a battery-powered emonTH (for example), apart from it often being necessary to exclude ambient light.