How it differs from the old 'verse.
Jasons' return was given a look in Batman Annual #25 and Red Hood: Lost Days, both written by Judd Winick. There's a time difference between the two as Winick states things taking a year in the first that take weeks in the second. Regardless it mostly stays the same. Superboy Primes actions bring Jason back to life in his coffin 6 months after he died. What's interesting to note for fans of time travel is the fact that Jason starts to regain all of his previous injuries from Death in the Family right after he comes back to life. He would have died--again--from the wounds but was found about a mile or so away from his grave. Since Bruce put all records of his family fingerprints and such under lock and key no one knew who he was. Jasons' mind was withdrawn to the point he can only function on his survival instincts to steal to eat and fight back when attacked. Someone notices his movements piecing together that he's Robin and the information gets back to the Al Ghuls.
Talia wants to help and Ras agrees since he's obsessed with death. Nothing they do helps Jason recover and Ras refuses to return Jason to Bruce or let him use the pit to heal. Since Ras plans on taking him away from her sight Talia dumps Jason in the pit and gives him everything he needs to make it on his own. Winick writes Talia more in character than Morrison but he still has her acting a little odd. Like kissing minor (and naked) Jason before shoving him off a cliff with his survival kit. Then giving the confused boy that just came back from a traumatic death triggering papers of Jokers' killing sprees, proof of Batmans' refusal to kill his murderer and even Jasons' death certificate. Winick has that moment as the one Jason gets overwhelmed by his anger and depression flying off into a rage. Although Lost Days has Ras suggesting the pit is affecting Jason and it's strongly hinted at him planning on killing the kid if he finds him for Talia "damning" his soul. He's certainly not pleased at his daughters' actions.
This makes it hard for Talia to keep in contact with Jason but not impossible. Fearing that Jason will kill her beloved Talia decides to stall him by sending him to various teachers. He collects new sets of skills while she foots the bills for everything. They met up when he's older and use each other in their grief. It doesn't seem to go the same way in DCnU.
Lobdell said that his backstory for Jason was just an extra bit of training that happened prior to Lost Days although there are some details that don't match up well. Of course a lot changed from the beginning of DCnU that the writers weren't aware of prior to their runs. It looks like a lot of Lost Days was dropped which I don't have a problem with. The first notable change is Talias' reasoning for training Jason, as she tells Ducra that she believes there's still a chance for Jason to become a good man. Although the All Caste are referred to as assassins (*1) their teachings deal with letting go of negative emotions. Unlike Winicks' version this Talia puts Jasons' welfare first. She's not doing this to try to keep him busy, she not even using his anger as a tool against Bruce. This was set up just to give Jason a chance at healing.
Since the Superboy Prime version isn't in canon anymore many assumed that Lobdell was using the pit as the means of his return as that's the first memory Jason has upon his return in RHATO #0. Eagle eye readers will note that's not the case as Talia tells Ducra that Jasons' body was fine when they found him (*2) but his soul was absent until they put him in the pit. (RHATO #2) Jason himself later confirms this as he recalls his past and says his previous state wasn't much more than a zombie since he wasn't all there. Ducra thinks the use of the pit might be something Ras would be pissed off at but Talia assures her that her father was "surprisingly supportive" of her choice. Since Ras previously punished his daughter and sent men to kill Jason it's another big change. Although it wouldn't shock me if this version had Ras being more accepting because he wanted to learn Jasons' secrets.
After Jason leaves the All Caste no other training is mentioned. The first thing he does after leaving is to attack mobs in Hong Kong to get the money he needed. That's another huge change as he's not letting Talia pay for anything and he doesn't have anymore of her help. It's not even certain if they have seen each other since she dropped him off.
*1 Their called assassins although the only ones they seem to train against are the Untitled, a group they weren't currently fighting because of a truce. No other enemy or targets has ever been mentioned. So basically they train Jason to kill but they don't give out assignments. Their not paid to kill either and have a strict code.
*2 I guess this means he didn't have the injuries he had in Winicks' version. Which kinda makes sense if their reducing the timeframe although Jasons' head wound was the reason for him being withdrawn from the world. Not having a soul until he was put in the pit is a new twist.