I have done this (transistor as diode, B=E) many times in IC
designs where I just wanted a plain old dumb 40V diode but
had a CAD group who just could not be bothered to add one
to the "blessed" library, and a modeling group who likewise
gave zero fvcks about making a decent model. So you get
to use what's on your plate. We would call this a "C-B
transdiode" (transistor (mis)applied as diode).
But the larger picture is still a mystery, it looks like the
PNP is used upside down as well and there's nothing to
indicate actual (let alone desired) function. Offhand it
looks like a waste of three components.