I believe USCIS typically notifies you when the case is transferred to a field office. However, I have asked live agents a few times, and they always say the case is at NBC. I would not be surprised if this is not accurate though.
Got EAD in about 40 days. Still waiting to get interview scheduled. Case at NBC. Receipt block IOE09309. The block seems to be getting processed at a quicker rate based on casestatusext.
Filed 3/25.