Thanks, 57. Your idea would certainly work.
I played around with the wiring last night and found that if I ran an optical cable from the Bell Fibe box to the home theater receiver, and then another HDMI cable from the home theater receiver output to the TV HDMI (ARC) input, that solved my problem. Now, I can either just turn the TV on and listen over its speakers or turn on the home theater receiver and listen over the surround speakers. An added bonus that I didn't expect was all three remotes' volume controls are synched. So no matter which remote I use, I can change the volume.
At any rate, thanks again for your help.