Yea if you go to barney's room and then noclip out of it, the actor for the general screens in the station changes to kleiner. Kleiner is the ruler of the combine for a minute there.
ive encountered that too! I thought it was strange that the combine would let an image like that on their screens... considering their relations with big K
It's because you can have unlimited TVs, but only one camera on at a time in source. So when you talk with Kliener, technically every TV in the game would broadcast his message. Same with anything else that appears on TV. You can't have two moving pictures at once.
but it's a pity that source has only one camera limit...
that would be cool to actually have few different pictures possible.
I think that this has to do with render-to-texture thingy and it's hardware limitations... but that's just my guess