How deep are Cordyline australis roots?

As its from Australia maybe they reach down to there? Probably no more then 2 feet deep though.

I Have just transplated one of these myself. It stands 12ft high from ground level, and the root was 4 ft deep below ground level. I dug round the trunk about 2ft in diameter, and flooded the rootball over night. A lorry with a hi-ab lifting arm was used to lift the tree straight up, and out of the hole. Roots were kept in perfect condition. Without this lifting equipment, i cannot see that a transplat of a plant of this size would be seccesfull.