The taxi that eventually picked me up was big enough for a
scooter, and your mom would have been able to ride sitting in it. The only possible problem would have been the length of the scooter. The back seat would need to be folded to fit a scooter in, reducing the number of seats for regular passengers. My wife had to ride up front with the driver.
Unless there are more wheelchair taxis on the road now (since my last trip September 2003) you will find it very, very difficult to get one, especially in the middle of the day.
Andrew