The Bodoy case that everyone quotes deals with one employee recording conversations with another in the workplace.

Not applicable here.

The Monica Lewinsky case was over the telephone.

Again, not applicable here.

The key thing here is "intercept", which O'Keefe and Giles did not do. Intercept is different that participate. Intercept means a third party not participating in the conversation.

Also, if I remember right from looking at the video, the door to the room was open, thus negating any expectation of privacy.