Well after playing around it appears that dat can be restored with "vol copy."  Here's what I used...
1 - create a new volume.
vol create dest_vol 100g aggrX  
2 - select the snapvault snap that you want to restore from.
snap list  source_vol
3 -  offline the destation volume before vol copy.
vol offline  dest_vol
4 - copy data from snapvaulted snap to new dest_vol.
vol copy start -s snapvault_snapshot.0 source_vol dest_vol
5 - bring the dest_vol back online.
vol online dest_vol