This is pretty easy, just take a look at the killcam.gsc in the mw2 patch look how it works. All you have to do is excute the playback to everyplayer in the game, than just that certain one.
i have looked in the mw2 killcam.gsc a long time ago.
I tryed to use the codes in a CoD4 patch but there are a lot of codes in the killcam.gsc wich are saved in other gsc example:
There is a code wich tells the game if the gamemode/map should have a final killcam. Its saved to every map/gamemode. I think it would not be easy ^^:p