Do Special MEA altitudes and routes in Alaska require WAAS?
The answer appears to be yes. The FAA document that describes this rule says:


  TSO C145a and TSO C146a GPS WAAS navigation systems are authorized to
  be used as the only means of navigation on Federal airways and other
  published ATS routes in lieu of ground-based navigation aids in Alaska


The IFR chart legend says:


  To utilize these routes aircraft will need to be equipped with IFR
  approved Global Navigation Satellite System (GNSS). In Alaska,
  TSO-145a and 146a equipment is required.


And both TSO C145 and C146 specifically mention WAAS in their titles.