156.180 is an old Plainfield Fire frequency that has been used for fire station tone-out and dispatch ever since Hendricks County went on SAFE-T. It is used the same as 154.130.
The 156.180 transmitter is in Plainfield while the 154.130 transmitter is in Danville. The 154.130 transmitter is more centrally located and runs more power. However, the problem with 154.130 in this area is that Brown County Fire has a repeater with the output on that frequency. The Brown County transmitter is on the big hill in Brown County State Park and you can easily hear it in Hendricks County. I guess Plainfield was worried that if the Brown County Fire repeater was transmitting at the same time a dispatch came out for Hendricks County, the Brown County repeater would win the RF battle, so Plainfield uses 156.180 instead.