There are numerous vehicles running on Butane in the country of Belize. We don't have statistics, but probably between 5% to 8%. Which means in this small country several hundred.
Belize gets Butane from nearby Mexico, so it is cheaper for farmers and towns near the northern Mexican border of Belize.
Butane is different than Propane found in the USA. The jet settings for the fuel and air mix are different. But easily adjusted as anyone with either a propane, or butane stove knows. Butane will smoke, if you do not change a propane stove settings with a screwdriver. Usually it means cutting off some of the air using a screw adjustable slide over the air intake.
The conversion apparatus is fairly simple in any country. The Mennonite farming community sell ready made off-the-shelf component conversion kits for gas engines to convert to Butane.