Some of you may know that I was recently in Chicago visiting family. At Howard station on the CTA, I got the usual no-photos spiel that the WMATA folks like to give. As usually happens at WMATA, they couldn't defend themselves when I challenged them on the rules, and watched as they gave nebulous arguments about "security". I would have won the argument had my mother not separated us, since she wasn't entirely comfortable about my putting transit employees ignorant of their own rules in their place off my home turf.
I find it all the more amazing in Chicago, since CTA expressly permits railfan-type photos, vs. WMATA where it's simply "not regulated".
Some NYC area fans have resorted to carrying copies of the photography rules to present to employees and/or police when challenged for taking photos.