I believe this circuit calls for using the same sort of analysis technique as would be used for an unbalanced resistance bridge, only here it is more like an unbalanced reactance bridge. Ground one end of the network, and apply a voltage source to the other. This circuit has 4 nodes in addition to the input & output (source & GND) nodes. Write 4 node equations using capacitive reactance Xc instead of resistance R. Xc = 1/(jωC) but since all currents will be capacitive in this circuit, it seems like it should not be necessary to carry through the 'j' in all calculations. And since the capacitance will not change as a function of frequency, select a value for ω that is most simple (ω=1?). Solve for the node voltages, find the total source current, and from that the equivalent reactance & equivalent capacitance.