Good that finally a study to evaluate the genetic diversity has been done across various sub-populations. It is interesting to know that the researchers have estimated that the lion-tailed macaques have separated into two distinct populations some 2.11 million years ago across the palghat gap. If the plantations are forced to mandatorily maintain a contiguous forest area around their periphery which is contiguous with other plantations then the movement of lion-tailed macaques and other animals would be easy. The original study can be downloaded from here.

The situation in the Annamalai hills can be seen in the documentary that I had done a couple of years ago https://youtu.be/Yr7twwnG3a8