I believe the AF won't take less than 1 year civilian service in an ICU to come in with the ICU identifier. We had one who came came in with only 6 months ICU - no lie on her part, recruiter may have flubbed a bit. The OIC didn't accept this and basically had her work as a shadow role until she went through the formal ICU course.
I think it also depends on the number if ICU applicant vs the number of ICU slots. If there's a bunch of experienced ICU nurses coming in, they're obviously going to get them. But of there are more spots than applicants, they may take on those with under a year experience. I know of one person here at COT that has less than a year ICU and they got the identifier. Its possible, but with competition getting more intense, it's going to only get harder.