How can I use my MVP210 and MVP110 using only one Static IP we are using SnapGear LIte+ on our network?

The MVP210 and MVP110 that are behind the Snapgear Lite+ will be able to call each other, if you use their private IP addresses when you create the phonebooks. They will not be able to share one static public IP address to communicate with other VOIPs over the Internet. The reason being the MVP110 and MVP210 use, largely, the same ports for communication. Either unit could, conceivably, initiate a call to a VOIP that is outside the firewall. When the answering VOIP sends packets back to the static IP, the Snapgear will be unable to ascertain which of the two voips these packets are actually destined for.

Each model would need its own static public IP address and the router must allow you to map ports coming from different external IP addresses to different internal IP addresses.