It doesn't look like the Start-NcVolMove cmdlet itself supports the necessary aggregate encryption parameter (-encrypt-with-aggr-key), unfortunately. However, the API that the cmdlet calls - volume-move-start - does. You can use the "Invoke-NcSystemApi" cmdlet to make the API call directly to work around the gap. Something like this might work:
$SourceVol = <your volume>
$DestAggr = <your destination aggregate>
$Vserver = <Source Vserver>
$Request = @"
Invoke-NcSystemApi -Request $Request
I don't have a system with NAE enabled to test this on, so I can't fully validate that it will work, but it should.