Actually, it was Sunspot that the scagworks were previously mentioned in, not Desert Kings. Both Sunspot and Apocalypse Unborn were written by the same author, and AU was intended to be published first. However, once the m****cripts were delivered GE made the decision to flip them because they had mistakenly scheduled two Doc Tanner time travel books back to back. Point in fact, the author was trying to do exactly what you are complaining about - create some continuity between books. He even warned the editors of the continuity issue when they desided to flip the schedule and was told that it had been "fixed". Clearly it was not.
As to whether the writers in general know anything about the other books - usually not. They are writers for hire, they are being paid a pittance to churn out x number of pages by a certain date based on a general plotline. At present there are 84 published books in the Deathlands series, and no rational human being is going to read roughly thirty thousand pages of pulp fiction in order to write a new entry. Making it even more complicated, they are writing the books long before they are actually published and there are multiple authors involved. This means that Writer #1 has no idea what Writer #2 is doing with the book being published immediately before theirs or what Writer #3 is doing with the book being published immediately after theirs. This makes book-to-book continuity very difficult. You could argue that there should be more editorial involvement and/or more communication between authors, but for a myriad of reasons this generally does not happen.
It is different when you have a series that is primarily written by a single author. For several years Deathlands was written by Laurance James, and he was able to weave long-running plot threads because he knew exactly what was happening book-to-book and could plant the seeds for future plots. With Deathlands moving to six per year, this situation is likely to only get worse. A given writer may be contracted to write several books, but they will likely not be published consecutively so the best they can do is weave some kind of general continuity between their own books while not hamstringing the other authors in the stable.
"Sadly then I knew the answer. All her life she was a dancer, but no one ever played the song she knew." - The Residents