The two-second answer (which is all the time I have at the moment) is that MNE can be embedded really easily with PyCall. There are a couple of gotchas (e.g. MNE’s Info class is a subclass of dict, which PyCall too aggressively converts to a Julia Dict, which eats the extra methods there, but this is easy to work around), but everything works fairly smoothly.
I think Julia native EEG functionality would be great for a lot of reasons, but it’s very convenient to be able to lean on MNE and the Python EEG ecosystem when a feature isn’t available.