This outdoor arena stage was in the area now occupied by the T2:3D show building (on top of the parking structure). Adjacent to it was the Fievels Playland area.
The set design for the show was all scaled so that the performers in mouse costumes looked tiny. These exclusive photos from 1990 show how well the illusion worked.
The "lead" mice had animatronic eyes and mouths which were operated by the dancers themselves (via triggers in the gloves). Tiger the cat was a mechanical puppet. He was operated by three people; one on each arm and a third buckelled into a chair sitting in the torso who could move the head using handlebars and control the mouth, eyes and eyebrows through a series of cable triggers much like the brakes on a bicycle.  The operator on the cat's right arm had a cable control that could open and close the bottom two of Tiger's four fingers. 
This allowed him to point and approximate holding on to Fievel
during parts of the show. The show was performed to a pre-
recorded soundtrack (download below).
Fievel can still be seen around the park as part of Streetmosphere.

NEW:Download the soundtrack for An American Tail Live
MP4 File (Quicktime) / Windows Media - 14m30s