It depends. Most regionals do not do this anymore because they found it was disastrous to do this with people who have never flown a jet. The Law of Primacy, it was like asking them to learn calculus before they knoew any algebra and trig.

Some places like Spirit still hand out stuff they expect you to know day one. Most everybody hired there has jet and part 121 experience. I realize that they may have started hiring CFIs, but I am sure the ability to self study is carefully assessed during the selection process.