AFAIK, this works the same as it does for filegroups without Filestream.

You can see some backup and restore here: http://www.mssqltips.com/sqlservertip/1854/how-to-backup-and-restore-a-sql-server-filestream-enabled-database/

I haven't tested a filegroup restore, but you should be able to do this, but it would follow the rules for filegroup restores: http://support.microsoft.com/kb/281122