It will work if you have a MVoip on both ends.
Analog out of the IPO to the MVoip, MVoip to MVoip Trunk to the remote office, then analog out of the second MVoip.
MVoip as a H.323 device off the IPO is not supported.
This method will work with any phone system that supports Analog (any that don't?) I've done it with a partner system....