Code 350 is for Bear activity. You will hear the refer to it as a "350 Jam" meaning cars are stopped looking at the bear and backing traffic up on the road, other times they just say Bear Jam.
Unit #:
700 is Park headquarters just outside of Gatlinburg
400's are your law enforcement people (Encryption is used periodically)
600's seem to be road crews
300's I believe are maintenance units
500's are on the North Carolina side Welcome Center area.
Also here is a link to Goggle Maps where I created a layout of the repeater tower locations.
http://maps.google.com/maps/ms?hl=e....583618,-83.531799&spn=0.568473,0.883026&z=10