I didn't write this script but forgot who on JamfNation posted it so I can't give credit. I am using the below on a login trigger with the $4, $5, and $6 variables populated in the policy. I adjust the scoping based on who needs to mount the volumes.

I am currently using:

#!/bin/sh

currentUser=$(ls -l /dev/console | awk '{ print $3 }')
    echo "Current User: $currentUser"
UID1=$(id -u $currentUser)
    echo "UID: $UID1"
protocol="$4" # This is the protocol to connect with (afp | smb)
    echo "Protocol: $4"
serverName="$5"   # This is the address of the server, e.g. my.fileserver.com
    echo "Server: $5"
shareName="$6"    # This is the name of the share to mount
    echo "Sharename: $6"

if [[ "$UID1" -lt 1000 ]]; then
     echo "$currentUser is a local user. This script will now quit"
     exit 1
fi

if [[ "$UID1" -ge 1000 ]]; then 
echo "User $currentUser is an Active Directory account"
# Mount the drive
mount_script=`/usr/bin/osascript <<EOF
tell application "Finder" 
activate
mount volume "$protocol://${serverName}/${shareName}/"
end tell
EOF`
fi