Just read it on todays ST (5 Dec 07).
They just sent the proposal to LTA. There is a test LPG taxi running around but I have not seen it.
It's slightly more expensive than CNG. Like CNG cheaper than diesel and petrol.
Delivery system is the same as CNG except that there is an evaporator instead of a pressure regulator. Cylinder is a tank and in this case, you can sacrifice the spare tire and put in place what is called a toroidal tank that fits the spare tire well. So you don't sacrifice boot space.
Refilling is at Union's bottling plant in Tuas.