It obviously took a long time to get information from one place to another. Let alone get the details of the strategy used by the Carthiginians. I also find it hard to believe that Hannibal nor his relatives wouldn't have spotted the fact that the Romans were using similar tactics that they themselves were using.
Scipio was a military tribune at Cannae and traditionally is said to have saved his father's life at the Ticinus. It's also not as though Hannibal's tactics came out of nowhere. Hannibal may have been a master of it, but encirclement, ambushes, and the rest of the tactics that both Hannibal and Scipio employed are as old as warfare itself. Nor was there any sort of "operational doctrine" regarding Hannibal of the other Carthaginian leaders for them to notice the Romans "copying," to whatever extent you can say that the Romans did
Sub Question. Did Scipio Africanus actually fight at Cannae or Trebia? I have thought that we was one of the survivors of Cannae perhaps as a military tribune, but I cannot remember the sources for the life of me.
Also, don't forget that Scipio was in Rome for 6 years (after the battle of Cannae), likely hearing the reports from the field and hearing more information from the patrician social circle of how Hannibal was running his campaign. Furthermore, down the road, Scipio would win over key Carthaginian allies, i.e. Massinisa, who could provide even further insight into Hannibal's tactics. Plus, it wasn't as if all the tactics that Scipio used were exact mirrors of Hannibal's. Scipio was far more prolific at winning over enemy allies than Hannibal was, thus undermining a crucial supply of troops. *Edit: clarification on comment