It's not uncommon for Engineers/Approved Mechanics to taxi aircrafts in North America. Infact most of the time, it was the only convenient way to get an airplane at the other side of the airport especially when airport is busy. Provided proper training and approval is held. I had to undergo run-up and taxi courses from the manufacturer which included sim time and was checked out by the chief pilot.
Some companies give out extra license premiums for taxi authorisation, not much I hear. I can tell you this, driving the A330's was a sure delight
Macdu