My only knowledge of the senshusei program comes from "Angry White Pajamas", a book I enjoyed, but is apparently disparaged by Yoshinkan folks. My understanding is that a student can enter the program without having any background in the arts and that the course is (by my definition) brutal. I am neither justifying or defending it. It seems that they take pride in their injuries in that course and that it is considerably different in flavor than regular Yoshinkan classes. After reading the book, I became convinced that I didn't want to train in that program (not that it was actually a possibility) and was very happy where I am. Maybe my limited perception is all wrong, but I would think that crippled Tokyo Riot Police officers wouldn't be all that handy to have around.
I know 2 people who are doing this currently and have met several graduates of this. I can confirm that they can do some big waza and take some wild breakfalls. But I donīt get the feeling from any of them that they actually know Aikido or what I consider as such.
Just my 2 yen worth.