It doesn't exactly appear in the novel. In my opinion, there are two possibilities.
For the first, Dr. Lui Kiu-chung may choose him as the right person to acquire the 'Ensemble'. Lui was looking for his colleagues - members of Cannon - who had 'loyal mode' implanted. Nick would have been one of the candidates, then it's quite natural that Lui approached Nick in ASR. Lui's $500,000 compensation to Nick is not just a goal of acquiring the Ensemble, but also a reward for his mission to find Laura.
The second is Laura's own assignment. Laura is described as having a macroscopic vision of humanity, which may have given mankind the choice to run the Ensemble.
The second theory is delicious to my taste, but logically, the first one would be right. To sum up, I think Lui would have done that.