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I'm trying to figure out more about exactly how this circuit works, specifically why terminal B responds the way it does.
A 12V zener is being used to generate a 12VDC supply (between terminal A and B in the schematic.) I have run simulations of the circuit to look at V(A)-V(B) and see that this parameter increases a few tenths of a Volt (up to 12V) only on the upswing of V(A) and remains constant on the downswing. I was just wondering why and if it is easy to calculate the behavior?

It's just a confusingly drawn diode pump with a series source resistor to limit the pulsed current drawn from the mains (and to limit the current through the zener):

For a laugh, see what happens if you:

i) remove the zener

and/or

ii) look at the current through R1 as you reduce it.

:)

See also:

https://www.circuitlab.com/circuit/3bqfj6/diode-pump-01-negative-output/

https://www.circuitlab.com/circuit/bww5sc/diode-pump-02-positive-output/

http://en.wikipedia.org/wiki/Voltage_doubler

http://en.wikipedia.org/wiki/Voltage_multiplier

http://www.micrel.com/_PDF/App-Notes/an-1.pdf

http://www.electronics-tutorials.ws/blog/voltage-multiplier-circuit.html

and very closely related because your diodes are operating as switches but with a voltage drop:

http://www.analog.com/static/imported-files/tutorials/ptmsect4.pdf

Zener diode is basically use the broken of voltage and it could be filterized supply send to other components.