No this is different. I assume you are talking about skip bin...

No this is different. I assume you are talking about skip bin trucks - ie large steel bins for building waste , soil etc not domestic garbage trucks.

This is a safety measure as driver is out of the truck using remote control to load truck or in and out of truck lowering boom/ hook / chains and aligning truck often in some area on steep roads or driveways or building sites . A hook truck pulling a 20 tonne skip has issues as brakes simply don't work as well in reverse as forward and under constant load park brakes can creep. Ie drags truck back to skip rather than skip to truck. as a example. Yes that can be used as a dangerous strategy o get extra heavy skips onto trucks but .... well... moving truck , loads off ground... danger will robinson danger

Current brake at price they indicate can not be wheel brakes IMO. So must be a driveline brake ( single unit) on the tailshaft I think.

Their previous garbage truck brakes was the full brake on all rear wheels ( large expense) and was there to not only provide less maintenance but to stop the noise from squeaky brakes. Garbage trucks are unique in that they stop start from 5km/h- 20 km/h constantly moving bin to bin so there is very short duration low speed application so not the intense heat that creates wear and fade from other applications where it is high speed braking or long duration downhill braking. . A key thing with garbage truck brakes is they do thousands of cycles so the pieces in linkages etc wear. Hydraulic air over disk should be a massive winner if set up right as liquid brake fluid is teh actual linkage for the majority of parts not metal to metal.