Apple could probably figure out if this data came from an app developer because I'd bet there's only exactly one app which every single one of those 1,000,001 devices downloaded.
Even if they threw in a few fake rows to mess up the data, they could find the app that has the highest percentage of downloads from that entire data set.
I can't think of any apps that take a full address. Perhaps there are some, I just don't know them.
Apple could have been compelled to release this data to the FBI. Unfortunately, we're unlikely to ever know this and Apple are equally unlikely to want to shed light on it.
If the claim is true, that the source data included full postal address, then I find it hard to identify a better source for all of that than Apple themselves. And that the data was brought together from various systems, and that we're glimpsing data that was shared between Apple and the FBI.
Not to say that there's anything illegal about that, more that the laws that allow that are a bit screwed but that's another issue altogether.
A reasonable assumption, besides Apple, is Facebook. With all the information these services have the easiest part may be to acquire your home address.
Another more likely possibility would be to identify people who are on the list and compare all their installed apps and search for a common denominator.
People delete apps though, you'd need their entire history to cross reference that. Not to mention false positives - how many people have the Twitter or Facebook app installed, for example?
You might still be able to find an app that has a much higher installation rate for users on the leaked list that for users who aren't.
Of course, that wouldn't be a proof but merely a first step to narrow the possibilities.
Even if they threw in a few fake rows to mess up the data, they could find the app that has the highest percentage of downloads from that entire data set.