Not to my knowledge. Maberry has occasionally referenced SIGMA Force from James Rollins's books and Seal Team 666 from the series of the same name by Weston Ochse. Jack's appearance marks the first time another author's character has appeared "onscreen" in the Ledger series.
For my part I see Maberry's setting as a kind of ultimate action-horror crossover world. You can assume that something like what happened in the various other authors' books happened here, but not that exact thing. So you don't have to read Nightworld and wonder "Why didn't Joe Ledger and RTI show up for this?"
"The most dangerous man, to any government, is the man who is able to think things out for himself. Almost inevitably, he comes to the conclusion that the government he lives under is dishonest, insane and intolerable." - H. L. Mencken