In case I ever need to refer to this, as I frequently take photos wherever I happen to wander, including CTA platforms.
CTA Photography Policy The general public is allowed to take snapshots in public areas.
Equipment such as lighting, tripods, cables, etc. is not allowed – except in instances where commercial and professional photographers enter into contractual agreements with CTA.
Photographers are not allowed to enter or photograph non-public areas of CTA stations.
Photographers are prohibited from obstructing transit operations, interfering with customers and blocking doors or stairs.
CTA personnel may evaluate the actions of photographers on a case by case basis to determine if a photographer is in compliance with guidelines. If a determination is made that the photographer is not in compliance, CTA personnel may ask them to stop.
[From CTA | Chicago Transit Authority - What's New]
Though the phrase, "obstructing transit operations" is slightly vague. Especially since it is the CTA personnel who decides.
[[or photograph non-public areas of CTA stations]]
This portion is a complete violation of ones civil rights. With the exception of a few military areas, photographing /anything/ you can see from a public space is protected.
Yes, but when two burly CTA guards come bumping up against you, what are going to you? Similar to getting asked by building security guards (like at Boeing, or elsewhere) not to take photographs from the public sidewalk "because of 9/11".
BS, but have to pick your battles.
It has been my experience with the CTA that if you are quick and discrete, nobody bugs you.