I believe its a PRI or CAS circuit that you have terminated on the VWIC. Yeah your PSTN circuits (PRI or CAS) can terminate directly on to the VWIC. You will need to add the router with this VWIC as a voice gateway (either use H323 or MGCP).
I bet you either have an IPLC or VPN from India to US. Either ways its a best practice to setup your remote office phones (India) to talk g729 codec while sending calls across to the US to save bandwidth to accomodate more calls.
If you do this, your phones in US will be in one region, while your phones in India will be another region. Now if you plan to do a conferencing between three phones (say one from each region) you will need a device called transcoder to translate the codecs. Typically you can use a 2600 with NM-HDV or NM-HDV2 for transcoding.
Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus