Never heard the term. Around here once you're hired, finish new hire orientation and pass third rider field training under an FTO, you're considered fully qualified to attend in the back. At my current agency you have to pass an EVOC course to drive, and since that's run by the police department, sometimes it can be months before you can go through. I was lucky, my class got EVOC while still in field training and were able to do both, drive and attend as soon as we hit the line, typically swapping out with our partner every other shift who drives and who attends all shift. The current class however has been cleared from field training about 3 months now and haven't been able to get EVOC scheduled yet so they've been effectively limited to only attending this whole time.
So basically, get your county EMT certification, apply, take and pass an EMT-Basic written test (Scranton, neighborhood of ~100 NREMT style questions), pass an oral interview board, pass a background check (complete with polygraph and field investigation), pass a chief's interview, physical exam, get uniforms, pass a two week new hire orientation academy, then 6-10 field training shifts and boom, you're the attendant in charge.
I can only imagine specific AIC training and certification is most likely run by the specific agency, and is probably regional as to where agencies even have specific AIC training or not.