I was a CG recruiter as well as a member of the USCG TRACEN admin/training staff. I was very familiar with this program as well as offered a direct promotion to E5 in this program myself.
What are your questions? Goal?
There is a application process that reviews qualifications along with how it aligns with CG qualifications, expertise and needs of the service. This is most common in medical, aviation, electronics and a few other fields.
I can tell you that my enlisted CG time, experience, expertise, and education earned me a direct commission in another service.
(I did not enjoy this other service as I was used to getting things done, not a hurry up and wait person) I worked with 3 of our other services and respect them all. We did have a special relationship with our Corps brothers though.