Domain Join >>>Suggestion

You could do it with a script that gets the site info using the API and pulls out the organization code. Using a case statement with a default domain run a policy based on org. code. This is rough and completely untested but it should give you the idea. As I used to hear in the Army this is "A" way not "The" way. Hope it helps.

#!/bin/bash

apiuser="username"
apipass="password"
jssurl-"https://your.jss.address:8443"

# Get the computer serial number
deviceSerial=$( ioreg -rd1 -c IOPlatformExpertDevice | awk -F'"' '/IOPlatformSerialNumber/{print $4}' )

# Get computer site info
computerSite=$(curl -H "Accept: text/xml" -sfku "${apiuser}:${apipass}" "${jssurl}/JSSResource/computers/serialnumber/${deviceSerial}" -X GET 2>/dev/null | xmllint --format - | grep -B1 "</site>" | awk -F'>|<' '/<name>/{print $3}')

# Pull the first 3 characters from the site info
orgCode=$(echo $computerSite | awk '{print substr($0,0,3)}')

# Based on the orgCode run a policy to bind to the domain
case $orgCode in 
    100) jamf policy -event bindto100 ;;
    200) jamf policy -event bindto200 ;; 
    300) jamf policy -event bindto300 ;;
    *) jamf policy -event bindtoDefault ;;
esac

exit 0