I can answer that because we coded up a special mode where we can respond to a device as if it supports multiple calendars (a la iPhone), even if normally the service wouldn't. I tried that with the N900 and unfortunately no luck -- the device's MfE only supports syncing one calendar. Perhaps the MfE developers can add this feature. It wouldn't be too hard I think since MfE already has the necessary folder support for email, and the device has multiple calendars.