I'm assuming those speakers are analog input only?
It probably doesn't, but check to see if your TV has an analog audio out. If it does, it should be as simple as connecting your FiOS STB and the AppleTV into the TV, then connecting the speakers to the TV.
If the TV doesn't have an analog audio out, then you would need something like this to switch between the two (use only the audio portion of the switch):
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www.amazon.com/RCA-DT902 ··· o+switchOr, probably a more sensible thing to do, acquire a speaker system with digital input. Either a PC speaker system that has digital input compatible with the digital output of your TV (optical or coaxial), or purchase a home-theatre-in-a-box (cheaper than buying all separate receiver + speakers).