Doug,
This wouldn't be considered a mast. Therefore, you needn't worry about approved support fittings or conduit size, other than normal NEC requirements.
As Bill points out, as long as the service drop is attached to the structure and not the pipe, this should be treated the same as any conduit run, with the addition of proper bonding for service raceways, per NEC 250.92
[This message has been edited by Redsy (edited 09-08-2003).]