Turnouts (when the jetway or boarding bridge goes as far back as possible) are common in many cities, especially at smaller airports. A turnout's only issue is that it tends to blow FOD (foriegn object debris) out of their crannies and onto the ramp, so while it may be faster, the rampers and marshaller have to do a visual inspection of the ramp after the aircraft departs. the aircraft also needs to be pointed at at least a 20 degree angle to the terminal inorder to do it successfully.

For a powerback, almost *AnY* plane can do it, including turboprops. They are faster than using a tug, but the only issue with powerback is 1. do you want to burn up that much fuel 2. is the ramp dry enough to allow it 3. braking action. Powerbacks are common with tail mounted jets (DC9s, 727s) but they can be done by 747s, MD 11s, DC10s, L1011s, but it just burns up so much fuel doing it, that it isn't done. (FYI, all engines have thrust reverse).

-nate