Hi
if branches are WAN connected u need to:
1-configure PIM all devices carrying traffic to ur branches from HQ site.
2-decide on which PIM mode u need sparse or dense ( maybe sparse-dense if u will use autodiscovery RP).
3-choose an RP is u choose sparse mode.
4-make sure there is a route for teh source.
Once you do this, multicast will be forwarded to ur branches regardless of Multicast address.
I suggest you read up a bit more on Multicast configuration, it shoudl be straightforward.
http://www.cisco.com/en/US/tech/tk828/technologies_tech_note09186a0080094821.shtml
HTH
Sam
