Hmmm ... is that a real, statutory wiretap? Like, to an actual and regulated telecommunications provider? Or is DOJ skating by on "quacks like a duck" orders? CALEA was limited for a reason (I imagine they really want to change that).
AFAIK pen-register and similar wiretappy things are only applicable if you're a phone company, or very much like one. If you just ship an app and handle packets, that's a different story.
The article doesn't really provide many details so it's hard to tell. I don't think they can order a wiretap under CALEA since, like you said, that only applies to telecom providers. And even if they determined that WhatsApp was a de facto telecom, CALEA still has exceptions for end-to-end encryption.
AFAIK pen-register and similar wiretappy things are only applicable if you're a phone company, or very much like one. If you just ship an app and handle packets, that's a different story.