EMI/EMC Simulation using SMPS Software
For conducted emissions one can implement a model of an EMI test receiver in the simulation (as a postprocessor, taking simulated waveforms) and simulate the same things which one would measure in an experimental setup. A good model description of an EMI test receiver can be found e.g. in sections 2.5.2 and 2.5.3 of this thesis. Fig. 2.18 gives the model overview.
I am not aware of commercial simulation software to be able to do this. However, it is built into the open source simulator GeckoCIRCUITS but this is not Spice-compatible.
Such a simulation only makes sense if you properly implement all relevant parasitics (e.g. stray inductances, coupling capacitances, ... as mainly defined by PCB design) and the switching behaviour of the semiconductors, and choose small enough simulation time steps.