RDI (Relationship Development Intervention) Programme:- anyone used this?

Hi Everyone, I have a son (8yrs) who has been diagnosed as having Asperger Traits. His problems centre around his social interactions, constantant talking and concentration. We were aware of his difficulties from a young age and have worked with him to help develop an understanding of the world around him. most of the techniques we have been taught have focused around social stories, modelling and simplifying his environment. These have worked well but recently we have hit a brick wall as my son now relys on prompts and has limited flexibility. 

Recently I have been put in contact with someone teaches the RDI (Relationship Developmetn Intervention) Programme. Has anyone used this programme? I would be grateful for any information, thoughts, experiences? 

Thanks.