Well, putting a trace under a component, gives about the capacitance between that trace and component. Does the trace carry an interfering signal that would be better not to couple to it? Put a shield between them (e.g. use a multilayer PCB).
You will usually find plots of impedance or attenuation in CMC datasheets. These can be turned into an equivalent circuit, modeling the winding and core inductance, and the winding and stray capacitance.
Simply put the offending trace capacitance in parallel with, well, somewhere along that network, and you basically have your answer.
I would worry more about your description, than the CMC itself -- it's going into an instrumentation amplifier? What is the CMC going to do? It only provides a series impedance. If the amplifier has no impedance to ground then there's no attenuation across the CMC. Surely you mean to put some capacitors or resistors to ground, or something?
What interference are you expecting to filter, anyway? Is this part of your 200kHz eddy current system? Why not get a faster in-amp, that offers more CMRR at 200kHz? Is it transients from signal switching? Ambient noise?
Tim