Yes it can. The units were designed to be usable as loco-hauled coaches.
There are main res air and brake pipe connections behind the nose cone. And a switch on the cab back wall to select ''loco hauled mode' which activates a translator to convert brake pipe pressure to an electrical signal to control the EP brake on the 80x.
There is also an 'attended/unattended' switch which, in attended mode, allows a competent person to travel in the cab of the 800 and respond to things like passcomm activations and major faults by activating an emergency plunger if necessary. In unattended mode, a passcomm activation or major fault vents the loco brake pipe bringing the train to a stand.
The critical factors are a) the type of coupler, i.e., whether the adaptor coupler is in use, or whether the loco is fitted with a Dellner (as on some 57s) which determines the maximum speed, and b) whether the 80x has an auxiliary power supply from a functioning GU to provide lighting, heating etc. for passengers.
