Is a grounded/neutral wire (not grounding wire) required to be run to a subpanel that will supply only 240V (2-pole) devices?
Its fine, no different than the main feed to your house. NEC(1999) article 200 is  "grounded conductors" and 215 is "feeders". 


  "200-2. General. All premises wiring systems, other than circuits and
  systems exempted by sections ... 215-7 ..., shall have a grounded
  conductor that is identified in accordance with section 200-6. ..."


and so 


  "215-7. Ungrounded Conductors Tapped From Grounded Systems. Two-wire
  dc circuits and ac circuits of two or more ungrounded conductors shall
  be permitted to be tapped from the ungrounded conductors of circuits
  having a grounded neutral conductor. Switching devices in each tapped
  circuit shall have a pole in each ungrounded conductor."


Meaning that you need to use double pole switches and breakers. (that disconnect both wires, as opposed to common light switches that only disconnect one of the wires.)