As Jim (and many others) reported yesterday, Apple has published a transparency document, detailing governmental requests seeking information about individual users or devices.

At the very end of the main body of the report are these two sentences:

Apple has never received an order under Section 215 of the USA Patriot Act. We would expect to challenge such an order if served on us.

As stated in the linked article, if Apple is ever served with a Section 215 order, they will not (unless they are granted some relief) be able to publicly discuss that fact. But, if Apple continues to publish transparency reports, the sentences quoted above will obviously be left out. A bit of a canary in a coal mine. Good move, Apple.