Update: We've received an official statement from an HTC spokesperson on the situation with US Customs, and it basically confirms what was said to the Taiwanese stock exchange. Here it is:
“Each imported HTC model must be reviewed by Customs and will be released once Customs officials have completed the inspection. Some models have gone through inspection and been released to our carrier customers. We don't have the status of each specific device model at this time, but we are working closely with Customs. We remain confident that this issue will be resolved soon.”
There you have it - things are happening, but HTC is unable to confirm exactly what models are now getting through.