I ran into the same problem and came up with this solution:
Powershell
$RssScriptPath = "C:\myRssScript.rss"
$TargetSsrsServer = "http:\\localhost\reportserver"
$MyStringArray = "val1", "val2", "val3"
& rs.exe -i $RssScriptPath -s $TargetSsrsServer -v _myStringArray=$MyStringArray
Rss script (VB)
Dim _phrase As String() = _myStringArray.Split(",")
Dim _values As String() = _phrase(0).Split(" ")
For index As Integer = 0 To _values .GetUpperBound(0)
PublishReport(_values(index))
Next
I only tried with a strings, but you may be able to use the same strategy to pass other types.