Hi
You can create GRE tunnels between your locations with encapsulation mode as GRE so that you can have the communication between locations done through the tunnel...
Instead of having IPSEC tunnels you can consider these tunnels but they are just an encapsulation mechanism and doesnt provide any kinda security to your data...
If you are concerned about security to the data transfer being done between the locations better look out for IPSEC tunnels
regds