It's US Customs that holds packages coming from China.. and DHL would provide tracking information when it's shipped.. so you would see on tracking info that the item is being held in US customs. The shipper is the one who gets the tracking info at the time of shipping, anyone who has shipped anything knows this.
http://www.dhl-usa.com/en/express/tracking/tracking_faq.htmlAt one point they were talking about getting a company in HK to handle the customs issues. They need the export paperwork for China to be in order as well as the import paperwork for the destination countries. It's possible that the units are with a customs broker at the moment and not with DHL, in which case they would have a reference number but not a number which is useful for tracking.
Avalon only started posting about customs issues relatively recently which suggests that they haven't had a broker working on export licence issues all along (which is understandable given that they're a tiny outfit shipping small quantities). China could chuck a hissy fit and decide that they won't allow the technology to be exported. Customs processing will likely start slowing down around about now too.
It's definitely reasonable to expect an update from Avalon this weekend, even if that's only scanning in a redacted copy of the paperwork they have for the shipments.