ok sorry if this has been posted but i have looked and not found anthing about. when you enter teleporter C room at the bottom of the walkway stairs there are shelves and on the top shelf there will be a radio click X (or square) and it should start playing. i cant remember the exact words but it goes along the lines of:-

"test subject is in chamber. begin testing, oh m-get this cleaned up! test has proved unsuccessful, test subject has reduce to the same form as the other subjects....Get this cleaned up!" end tape

it is along those lines but some things in the quote could be wrong.
if a video is needed then i will be available to those with a capture card tomorrow.

EDIT::: this isnt really an easter egg but>>>> wehn entering teleporter B, Dempsey says "any ya ever heard of Die Glocke?"

EDIT::: a note "flagen sie dem gesamtplan" this means "follow the plan"