Detect Disabled SideChain?

How can I detect if the SideChain is disabled ?

This always returns a buffer with one (or several) channels even if I select no SideChain in the DAW (ProTools for instance) :
busArrangement.getBusBuffer(buffer, true, 1);

In theory this would be possible for AAX: when disabling a side-chain, ProTools simply changes one of the parameters passed to the audio rendering callback. This happens without suspending the plug-in first and could theoretically change from callback to callback. On the other hand, JUCE guarantees that setPreferredBusArrangement is only called when the plug-in is suspended. So, there is no good way to map this behaviour to JUCE land without an API change etc.

Any ideas or strong opinions on this?