It is an interesting system. Apparently it was developed by boxers because decades ago it was thought that black people couldn't take a punch. So the coaches trained them to block and evade as much as possible.
Things changed but you could see some JHR moves in Joe Louis and Mike Tyson.
The only place in the world where it is openly practiced is in Harlem, New York. However, there are some instructional videos around. Can't talk of the quality as I have never seen them.
Using the elbows to block is a classic pugilism technique, so I can see where it comes from.
http://www.youtube.com/watch?v=vmrp1scHTvE&feature=related