One thought would be to setup a phantom extension for this user on the local IP Office system. Set that user for unconditional forward to the remote location extension or DID and tick "Forward Huntgroup Calls". Add the phantom extension to the local hunt group. Incoming calls to the hunt group will ring the remote user as desired, assuming of course that the hunt group is set to circular or linear (doesn't work with Group or Most Idle). Assuming a 3.0 build and centralized VMPro, you could also set the hunt group voicemail to broadcast, and configure the phantom user to leave a voicemail at their remote extension (User "Leave Mail" action).
Alternatively, assuming a VCM at the local office, you can simply give the remote user an IP hardphone mapped to a VoIP extension at the local office. In such instance, you've got a few options to consider including letting them have two separate phones with different extensions - the VoIP phone being something of a "bat phone" for that hunt group you mentioned -or- configure the phantom user and unconditional call forward settings as noted above at the remote location pointing back to the VoIP extension thus allowing them to have just one phone.
At least a few ideas to consider anyways.
Erik