@Dramakus Sure. Just change line 12 from:
if {[lsearch -exact [channel info $chan] +google] != -1} {
To:
if {[lsearch -exact [channel info $chan] +google] != -1 && [isvoice $nick $chan]} {
Keep in mind that this method uses the irc module which keeps track of voiced users by recording mode changes.
In other words, if the bot didn't see a user get voiced it will not recognize him/her as a voiced user.