They're not. Pet RFID chips are low frequency and have a read range of a few inches at most. By the time you pump enough energy in to get a signal a foot away, you've probably microwaved the pet and blown out the chip antenna.

I think they bounce rf waves off of them. Same as with money, larger bills have a magnetic strip, they can bounce rf waves off of them and see how much cash is out there if not shielded.

I, like most people, didn't read the article. However, a lot of people use tracking tags on their pets collar so they can actually be tracked if they get out. I'm guessing that is what these cameras will be picking up.