We stayed at CBR in August/September 2003. We were in the main pool one night an could see some fireworks in the distance. I believe that they were Epcot's, but they were pretty far away. Not very impressive from there.
The funniest thing I saw when we were at CBR was the people watching the EPCOT fireworks, and leaving when they assumed they were over. I stood there, saying to people, "they're not over yet" (there's that whole "pictures on the world" sequence") ... "just wait a couple more minutes for the finale". Nope, they thought I was some nutty lady standing on the beach looking at an empty sky You can still hear the music. And then just as they would reach their building, the fireworks would start up again. "Not so nutty now, eh?"
Yes you can see the high fireworks of Illuminations at Epcot from several locations at CBR. Sometimes you can even hear the music. You can see some of the lower ones up at the Customs house also.
I agree about people leaving too early. We have mentioned it to leaving people several times.