Apparently CBS Outdoor considers atheism to be equivalent to alcohol or tobacco, unfit to be advertised near sensitive churchgoers or students.
They are probably within their rights to do this--they own the billboards--but their belief that this is a sound business decision is pretty absurd and cowardly. (I haven't actually seen the contracts, but I suspect they are crafted in such a way to leave themselves the option to move locations or even cancel the contract if there's a whiff of controversy that they'd prefer to avoid.)
I suspect the locations of the billboards are unlikely to make much difference about whether controversy is generated, but this change gives CBS Outdoor something they can appeal to in response to criticism--see, we tried to be sensitive to religious concerns about the expression of disagreement.
The new locations are likely to be approved on Monday, and I'll report here what they are. I'm actually surprised that there are any billboard locations in Phoenix that aren't within 1000 feet of a church or a school.
(Previously, previously, subsequently.)